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The antiferromagnetic orthoferrite YFeO3 possesses fascinating magnetic properties for spintronics, such as terahertz spin dynamics, ultrafast domain wall motion, and long magnon decay length. YFeO3 belongs to a special family of antiferromagnets that show an unusually strong non-trivial Kerr response due to its weak ferromagnetism. The highly stable antiferromagnetic domains without any spontaneous spin rotation transitions below the 645 K Néel temperature may be useful for nanoscale device applications. We report the successful fabrication of high-quality twinning-free (110)-oriented YFeO3 films by pulsed laser deposition. Detailed structural and magnetic characterization revealed that the crystal structure and magnetic properties of the YFeO3 films are comparable to bulk single crystals. We show that the spin rotation under high magnetic fields follows the two-sublattice approximation model. The film surface is atomically flat with step-terrace surface morphology. A longitudinal magneto-optic Kerr (MOKE) rotation of 10 mdeg was observed at room temperature, which is consistent with earlier reports on bulk single crystals. The in-plane anisotropy of the Kerr response corresponds to the obtained magnetic anisotropy from the SQUID measurement. The large MOKE signal enables the imaging of antiferromagnetic domains and their reversal. The domain size was found to be larger than 100 μm. These high-quality YFeO3 thin films facilitate the fabrication of antiferromagnetic spintronic devices and provide a convenient platform for studying various spin-related phenomena in thin films and at interfaces. [ABSTRACT FROM AUTHOR]

A key piece for spintronic applications, the so-called electron g -factor engineering is still predominantly based on the semiconductor bulk g factor and its dependence on the bandgap energy. In nanostructures, however, the mesoscopic confinement introduces exclusive anisotropies, transforming scalar g factors into tensors, enabling different renormalization mechanisms as routes for fine-tuning the electron g factor. These questions we address in this comparative theoretical analysis between the obtained electron g -factor (tensor) anisotropies for realistic InAs | AlSb - and In 0.53 Ga 0.47 As | InP -based multilayers. The electron g -factor anisotropy, i.e., the difference between g factors for magnetic fields parallel and perpendicular to the interfaces, is analytically calculated via perturbation theory using the envelope-function approach based on the eight-band Kane model. Effects from bulk, interfacing, tunnel coupling, and structure inversion asymmetry are systematically introduced within a transparent comparative view; differences between obtained anisotropies, such as in the magnitude, sign, and other fine details, are analyzed in terms of the heterostructure parameters, mapped over different confining and tunnel-coupling regimes without requiring elaborated numerical computations. [ABSTRACT FROM AUTHOR]

Nutation and precession resonances in an antiferromagnet subjected to a dc magnetic field are investigated by employing coupled linearized inertial Landau–Lifshitz–Gilbert equations describing the dynamics of magnetizations of antiferromagnet sublattices with uniaxial magnetocrystalline anisotropy. Analytical expressions for the eigenfrequencies of such an antiferromagnet are obtained for the longitudinal and transverse directions of the external dc field and for different ranges of its strength. The effect of inertia on the values of the resonant frequencies is shown for all possible states of the antiferromagnet in both the longitudinal and transverse directions of the external field. The estimated resonant frequencies are compared with those obtained from the numerical solution of the system of undamped inertial Landau–Lifshitz–Gilbert equations for closed trajectories of sublattice magnetizations. The good agreement of both independent estimations is demonstrated. [ABSTRACT FROM AUTHOR]

We report an investigation into the substantially large and customizable exchange anisotropy (HEA) and coercivity (HC) in a set of bottom-pinned Ir7Mn93/Co2FeAl bilayer heterostructures fabricated using ion-beam sputtering at room temperature (RT) in the presence of an in-situ in-plane static magnetic field of 1 kOe. This modulation is achieved by controlling the microstructural parameter (i.e., grain diameter) of the antiferromagnetic (AF) Ir7Mn93 (IrMn) layer. These bilayers revealed strong positive exchange anisotropy (PEA) at RT, while negative exchange anisotropy (NEA) became evident when field-cooled to 15 K in the presence of 3 kOe. By systematically controlling the AF grain diameter from ∼5.39 to ∼6.94 nm, the PEA and NEA were found to increase by a factor of ∼2.1 and ∼1.8, respectively. However, once the AF grain diameter exceeded the necessary threshold for thermal stability, further enhancement in grain diameter above ∼6.94 nm led to a reduction in both HEA and HC. This decrease was attributed to a reduction in pinning centers at the AF/FM (ferromagnet) interface. The training data are fitted by utilizing various theoretical models, such as thermal relaxation, Binek's model, and spin relaxation model. The spin relaxation model was found to be applicable to fit the complete range of training data, encompassing both thermal and athermal decay, within the context of frozen and rotatable spins. [ABSTRACT FROM AUTHOR]

There exists a controversy in the literature concerning the values of coercive and bias fields in antidots magnetic structures formed by a hexagonal network of nanoholes. The coercive fields (H C) and the exchange bias fields (∣ H E X C ∣) for antidots (deposited on ultrathin anodic aluminum oxide, namely, AAO) are either increased or diminished by comparison with the same magnetic nanostructures grown on continuous substrates (namely, CML). We propose to elucidate these debates by showing the importance of the easy axis of the magnetization, the direction of the applied magnetic field, the thicknesses of the layers, and the 3D-topology of nanoholes, as well as the magnetic and thermal history of the magnetic measurements. Here, biased Ta(5 nm)/Pt(5 nm)/Co(0.6 nm)/Fe 50 Mn 50 (X)/Ta(5 nm) antidots are investigated by extraordinary Hall effect measurements at 5 K, where X varies in the (0–5.5) nm range. The substrate consists in a hexagonal array of holes, described by the pair of (p , d) values, respectively, the period as the distance from center to center of two consecutive holes and the hole diameter. The dimensions of antidots are (p ≈ 100 and d ≈ 40 nm) for X = (2–5.5) nm, (p ≈ 150 and d ≈ 60 nm) for X = 3.5 nm, and (p ≈ 100 and d ≈ 60 nm) for X = 0. A continuous stack using Si/SiO 2 (100 nm) is used for comparison. H C and ∣ H E X C ∣ gradually increase when X is enhanced for both substrates, with nevertheless a weak decrease at high X for the continuous system. Perpendicular magnetic anisotropy is only observed for both unbiased samples, the X = 2 nm continuous sample, and both X = 5 nm samples that have undergone field cooling treatment from 500 to 5 K under − 2 T. Usually, H C (AAO) > --> H C (CML), ∣ H E X C (AAO) ∣ > -->∣ H E X C (CML) ∣ , and ∣ H A (AAO) ∣ <∣ H A (CML) ∣ (H A designating the anisotropy field). However, for certain conditions, as, for instance, for FC-procedures starting from high temperatures and/or strong magnetic field, other situations might be observed. A discussion pertaining to the amplitudes of H C , ∣ H E X C ∣ and the anisotropy field (∣ H A ∣) of continuous and discontinuous samples is given for our experimental results as well as for published data in the literature, in the light of structural characteristics (wedge-to-wedge distance, porosity, or coverage ratio). Such biased perpendicular antidots might be particularly used in specific nanomaterials devoted to spintronics. [ABSTRACT FROM AUTHOR]

Ferrimagnetic antiperovskite Mn 4 N has received growing interest due to room-temperature observation of large perpendicular magnetic anisotropy, low saturation magnetization, and ultrafast response to external magnetic fields. Comprehensive understanding of the underlying magnetic structure is instrumental in design and fabrication of computer memory and logic devices. Magneto-optical spectroscopy provides deeper insight into the magnetic and electronic structure than magnetometry. Simulations of a magneto-optical Kerr effect in biaxially strained Mn 4 N are performed using density functional theory and linear response theory. We consider three ferrimagnetic phases, two collinear and one noncollinear, which have been investigated separately by earlier studies. The simulated spectra are compared to measured magneto-optical data available in recent literature. One of the collinear ferrimagnetic phases is found to be consistent with the measured spectra. We show that an admixture of the noncollinear phase, which is the ground state of unstrained Mn 4 N, further improves the agreement with measured spectra, and at the same time, it could explain the lower than predicted net moment and magnetic anisotropy observed in thin films on various substrates. [ABSTRACT FROM AUTHOR]

H−T phase diagrams for chromium oxide chloride (CrOCl) are usually obtained using data from the measurements of magnetization and specific heats. Recent works suggest that magnetic anisotropy exists in CrOCl. In this work, we use dynamic cantilever magnetometry, which is sensitive to both magnetization and magnetic anisotropy, to probe phase transitions in CrOCl flakes. Together with magnetization measurements from a Superconducting Quantum Interference Device, four major regions of the CrOCl H−T phase diagram along its c-axis are obtained, which is consistent with the previously reported works. Then, we studied magnetic field induced transitions in CrOCl flakes under four different temperatures. Several transitions in antiferromagnetic state and in incommensurate state, which have not been reported before, were recognized. We believe these transitions probably originate from magnetic anisotropy due to magnetoelastic coupling and lattice reconstruction in CrOCl. Our work provides intriguing experimental results on the intricate magnetic structure of CrOCl, making progress in understanding the rich magnetic states of CrOCl. [ABSTRACT FROM AUTHOR]

In this article we analyze the thermal processes in magnetically anisotropic metal complexes under the action of non-adiabatic switching of magnetic field. Using the non-stationary perturbation theory for the case of sudden perturbation, we show that this field can cause not only heat release, but also heat absorption, interconnected with the axial zero field splitting (parameter D) in a paramagnetic metal complex. As an illustrative example we consider the simplest S = 1-complexes having "easy axis" and "easy plane" types of anisotropy influenced by the magnetic field that is suddenly turned off. We demonstrate that the character of the thermal processes (heat dissipation or absorption) depends on the sign of D and direction of applied field and so the analysis of these processes can be in principle used as a complementary tool (in addition to SQIUD magnetometry, EPR spectroscopy and INS) for studying magnetic anisotropy. The conditions under which the non-adiabatic switching of the magnetic field gives rise to the heat absorption are revealed. This unusual phenomenon, which can be called "nonadiabatic field switching cooling", may have practical applications. [ABSTRACT FROM AUTHOR]

Electric field control of magnetic properties offers a broad and promising toolbox for enabling ultra-low power electronics. A key challenge with high technological relevance is to master the interplay between the magnetic anisotropy of a ferromagnet and the exchange coupling to an adjacent antiferromagnet. Here, we demonstrate that magneto-ionic gating can be used to achieve a very stable out-of-plane (OOP) oriented magnetization with strong exchange bias in samples with as-deposited preferred in-plane (IP) magnetization. We show that the perpendicular interfacial anisotropy can be increased by more than a factor 2 in the stack Ta/Pt/PtMn/Co/HfO2 by applying −2.5 V gate voltage over 3 nm HfO2, causing a reorientation of the magnetization from IP to OOP with a strong OOP exchange bias of more than 50 mT. Comparing two thicknesses of PtMn, we identify a notable trade-off: while thicker PtMn yields a significantly larger exchange bias, it also results in a slower response to ionic liquid gating within the accessible gate voltage window. These results pave the way for post-deposition electrical tailoring of magnetic anisotropy and exchange bias in samples requiring significant exchange bias. [ABSTRACT FROM AUTHOR]

Millisecond pulsars (MSPs) are believed to be very old neutron stars (NSs) whose age may exceed significantly 108$$ {10}^8 $$ years. Although cooling scenarios of isolated NSs predict for that age a surface temperature Ts~104$$ {T}_s\sim {10}^4 $$ K, observations of the nearest MSP J0437‐4715 indicate Ts$$ {T}_s $$ well above that value. Besides the heating of the polar cap surface by backflowing charged particles, Joule heating in the crust can contribute to the overall heat budget of MSPs. Because the dipolar field component, derived from P$$ P $$ and P˙$$ \dot{P} $$ measurements, is much too weak for remarkable heating, smaller‐scale structures should be analyzed to understand whether they can supply the demanded heat. For this purpose, we study the small‐scale field structure of radio pulsars. Magnetic field components, significantly stronger than the dipolar one, may exist especially at the surface of MSPs. We assign upper limits to the strength of single‐field components up to a multipolarity of l=10$$ l=10 $$ and the corresponding deviations from axial symmetry m≤l$$ m\le l $$. Arguments are provided that the decay of the small‐scale components with l=3$$ l=3 $$ or l=4$$ l=4 $$ of the crustal magnetic field may cause the relatively high surface temperature of isolated MSPs. [ABSTRACT FROM AUTHOR]

The recently proposed magnetoimpedance tomography method is based on the analysis of the frequency dependences of the impedance measured at different external magnetic fields. The method allows one to analyze the distribution of magnetic properties over the cross-section of the ferromagnetic conductor. Here, we describe the example of theoretical study of the magnetoimpedance effect in an amorphous microwire with inhomogeneous magnetic structure. In the framework of the proposed model, it is assumed that the microwire cross-section consists of several regions with different features of the effective anisotropy. The distribution of the electromagnetic fields and the microwire impedance are found by an analytical solution of Maxwell equations in the particular regions. The field and frequency dependences of the microwire impedance are analyzed taking into account the frequency dependence of the permeability values in the considered regions. Although the calculations are given for the case of amorphous microwires, the obtained results can be useful for the development of the magnetoimpedance tomography method adaptation for different types of ferromagnetic conductors. [ABSTRACT FROM AUTHOR]

The interfacial Dzyaloshinskii–Moriya (iDMI) interaction which arises at the interface between a heavy metal (HM) and a ferromagnet (FM) can stabilize chiral Néel type domain walls in ultrathin perpendicularly magnetized multilayers. Dissimilar HMs are required on both bottom and top sides of the FM layer in order to introduce the structural inversion asymmetry which ensures an effective iDMI in the FM layer. HMs like Pt, Ir, Ta etc are very well known for developing large iDMI in the interface with Co, whereas noble metals like Au can produce negligible iDMI. Therefore, a multilayer Pt/Co/Au is chosen to determine the individual iDMI in the Pt/Co interface. Some procedures like field-induced domain wall motion study, spin–orbit torque efficiency estimation study are well established to quantify the effective field due to the iDMI ( H DMI ) which in turn gives the strength of the iDMI ( D eff ). Besides these procedures, a current-induced switching of magnetization was studied to construct a switching phase diagram where the critical current density of magnetization switching has been plotted as a function of the applied in-plane magnetic field. The experimentally constructed diagram and the simulated diagram using a micromagnetic study have revealed the possibility to quantify H DMI . Thus, a systematic and unified estimation of D eff has been done on all-metallic Ta/Pt/Co/Au multilayers. [ABSTRACT FROM AUTHOR]

Magnon Hanle effect in easy-plane antiferromagnets allows us to obtain different output spin states without switching the Néel vector, which opens up a different path for the construction of future magnonic devices. This effect originates from the precession of the pseudospin and is sensitive to the basic magnetic parameters, such as magnetic anisotropy, so that a precise control of magnon Hanle effect is needed. Here, we manipulate the magnon Hanle effect in easy-plane antiferromagnetic α-Fe2O3 with different film thicknesses and the resultant different strain and easy-plane anisotropy. The Hanle peak shifts to the lower magnetic field when the film thickness increase is associated with decreasing easy-plane anisotropy. The anisotropy–thickness relationship can be attributed to the strain relaxation by interfacial dislocations, which varies with film thickness. Our finding builds a bridge between magnon transport and material microstructures and provides a different perspective for the control of magnon Hanle effect and future magnonic devices. [ABSTRACT FROM AUTHOR]

Spin‐orbit torque resulting from non‐magnetic materials with strong spin‐orbit coupling enables electrically controlled magnetization switching, offering potential applications in ultralow‐power memory and logic devices. However, such switching of perpendicular magnetization usually requires an in‐plane magnetic field along the applied current direction, which limits its use. To address this challenge, an all‐oxide superlattice is designed and fabricated that show both the perpendicular magneto‐crystalline anisotropy and in‐plane magnetic anisotropies induced by interfacial engineering. The results demonstrate that the coexistence of perpendicular and in plane magnetic anisotropy breaks the symmetry and thus enables the pure electrical switching of perpendicular magnetization. [ABSTRACT FROM AUTHOR]

Magnetoelastic micro-electromechanical systems (MEMS) are integral elements of sensors, actuators, and other devices utilizing magnetostriction for their functionality. Their sensitivity typically scales with the saturation magnetostriction and inversely with magnetic anisotropy. However, large saturation magnetostriction and small magnetic anisotropy make the magnetoelastic layer highly susceptible to minuscule anisotropic stress. It is inevitably introduced during the release of the mechanical structure during fabrication and severely impairs the device's reproducibility, performance, and yield. To avoid the transfer of residual stress to the magnetic layer, we use a shadow mask deposition technology. It is combined with a free-free magnetoelectric microresonator design to minimize the influence of magnetic inhomogeneity on device performance. Magnetoelectric resonators are experimentally and theoretically analyzed regarding local stress anisotropy, magnetic anisotropy, and the ΔE-effect sensitivity in several resonance modes. The results demonstrate an exceptionally small device-to-device variation of the resonance frequency < 0.2% with large sensitivities comparable with macroscopic ΔE-effect magnetic field sensors. This development marks a promising step towards highly reproducible magnetoelastic devices and the feasibility of large-scale, integrated arrays. [ABSTRACT FROM AUTHOR]

We perform systematic studies on the magnetic and magnetotransport properties of Fe1/3NbS2 single crystal. Results show that Fe1/3NbS2 is an antiferromagnet with strong perpendicular magnetocrystalline anisotropy even in the paramagnetic state. The Fe1/3NbS2 nanoplate exhibits exotic magnetotransport characteristics with variation of temperature and magnetic field in the vicinity of Néel temperature. The temperature dependence of resistivity indicates that the magnetic field has a substantial effect on the Néel order of Fe1/3NbS2, and an intermediate phase occurs before the sample enters into the antiferromagnetic state. It is the field- or temperature-induced antiferromagnetic–intermediate phase and intermediate phase–paramagnetic phase transitions that lead to the novel magnetotransport characteristics in the vicinity of Néel temperature. The findings in this work will promote future studies based on two-dimensional antiferromagnetic spintronics. [ABSTRACT FROM AUTHOR]

A giant magnetoresistance (GMR) sensor with a Wheatstone bridge structure and an out-of-plane linear response was developed. The spin-valve structure consists of a synthetic antiferromagnetic [(Co/Pt)n/Ru/(Pt/Co)n] reference layer with perpendicular magnetic anisotropy, a Cu spacer layer, and a Co-free layer with in-plane easy magnetization. By utilizing the spin–orbit torque induced magnetization switching in the synthetic antiferromagnetic layer, the magnetization of the reference layers in the adjacent bridge arms is set to the opposite direction, achieving a GMR sensor with a full Wheatstone bridge structure. The sensor exhibits linear response to the out-of-plane magnetic field with adjustable dynamic ranges from hundreds to thousands of Oe, depending on the thickness of the Co-free layer. A similar Wheatstone bridge sensor consisting of magnetic tunnel junctions was also proposed. The sensor with out-of-plane linear response may have promising applications in three-dimensional magnetic field detection and current sensing field. [ABSTRACT FROM AUTHOR]

Deterministic spin orbit torque (SOT) magnetization switching of the perpendicular magnetic anisotropy structures requires an external magnetic field, which is unsuitable for on-chip applications. Various approaches are there to debar the external magnetic field requirement. In this work, we use static stress, which can generate a virtual magnetic field via magnetoelastic coupling. We show that this field can be used for deterministic magnetization switching. In our simulations, we use an antiferromagnetic material for generating the SOT and exchange bias field and avail the benefits of the field like torque (FLT). With the exclusion of thermal noise, this reduces the threshold current density from 114 to 36 MA/cm2, thus mitigating the energy dissipation by more than nine times. To study the effect of thermal noise, we simulate 500 trajectories and find out the switching probability. We perform simulations to study the effects of current density, stress, pulse width, and FLT on the switching probability in great details. Our simulation results show that we can get sub-ns switching with a probability of 0.99 requiring only 45.5 fJ of energy dissipation. This can be very attractive for artificial neural network kind of applications. [ABSTRACT FROM AUTHOR]

Angular-dependent magnetoresistance (ADMR) of an epitaxial Fe(001) film is investigated with current along hard and easy axes in-plane at different temperatures. The temperature dependences of ordinary magnetoresistance (OMR), anisotropic magnetoresistance (AMR), and magnetocrystalline anisotropy magnetoresistance (MMR) in ADMR were determined. As temperature decreases, negative OMR and positive AMR with a twofold symmetry show increasing and decreasing amplitudes, respectively. The amplitude of MMR with twofold and fourfold symmetries is almost invariable with both temperature and magnetic field. Meantime, when current was applied at hard and easy axes, MMR contributes an anti-phase signal to ADMR. Our findings of OMR, AMR, and MMR in the Fe(001) ADMR are of great significance to the understanding of magnetoresistance in magnetic films. [ABSTRACT FROM AUTHOR]

Spin torque oscillators (STOs) are emerging microwave devices that can potentially be used in spin-logic devices and the next-generation high-speed computing architecture. Thanks to their non-linear nature, STOs are easily tunable by the magnetic field and the dc current. Spin Hall nano-oscillators are promising types of STOs and most of the current studies focus on localized modes that can be easily excited. Here, we study using micromagnetic simulations, the nature of the spin-torque-induced excitations in nanowire devices made of perpendicular magnetic anisotropy (PMA) materials. Our results showed that, upon including PMA, the excitation of localized and propagating spin wave modes is feasible. We study the nature of the mode excitations as a function of the PMA strength ( K u) and the current. Indeed, we estimate a critical value of K u to allow for the excitation of the propagating spin wave. We attribute this mode selectivity between localized and propagating modes to the magnitude and the change of the sign of the nonlinearity of the system from negative to positive at a non-zero K u , which is supported by analytical calculations. Our results provide deep insight into engineering microwave devices for future magnonic and computational applications. [ABSTRACT FROM AUTHOR]

As a kind of magnetostrictive ceramics, cobalt ferrites are widely concerned because of its large magnetostriction and high resistivity, which are ideal for high-frequency applications. But, the high driving magnetic field due to the high magnetocrystalline anisotropy limits the practical applications of cobalt ferrites, thus, it is a still a challenge to find a balance between high magnetostriction properties and low driving magnetic fields. In this work, we investigated the effects of partially substitution of Ga3+ for Fe3+ on grain orientation and magnetic properties, attempting to maintain high magnetostriction while reducing the driving magnetic field. The CoFe 2-x Ga x O 4 (x=0, 0.05, 0.1, 0.15) with single-phase spinel structure were prepared by the conventional solid-state method. The saturation magnetization M S increased with the increase of Ga concentration, meanwhile the coercivity H c and magnetocrystalline anisotropy constant K 1 significantly decreased, which indicates the better soft magnetic characteristics of the Ga-doped cobalt ferrites. The oriented CoFe 2-x Ga x O 4 samples were obtained using magnetic field orientation technique during the powder forming process. The <001> preferred orientation was achieved in CoFe 2 O 4 samples. However, the <001> orientation degree decreased with the substitution of Ga, and the preferred orientation has changed into <111> at x=0.15. The Ga substitution affected the magnetocrystalline anisotropy and grain orientation, thereby affecting the magnetostrictive properties. As for the non-oriented samples, although the maximum magnetostrictive strain slightly decreased with Ga substitution, while there was a significant drop in the magnetostrictive saturation field. However, the magnetostriction of the oriented samples decreased significantly with the substitution of Ga due to the change of grain orientation from <001> to <111>. [ABSTRACT FROM AUTHOR]

We present femtosecond-pulse-induced precession of magnetization at low laser fluence (< 5 μ J / cm 2) regime as a function of magnetic field and laser fluence in three Co/Pd multilayer (ML) systems. These systems belong to three different regimes of magnetic anisotropy that vary with Co thickness (t C o ): in-plane (sample 1, t C o = 0.74 nm), weakly out-of-plane (sample 2, t C o = 0.6 nm), and out-of-plane (sample 3, t C o = 0.40 nm). Interestingly, we observed that the precession amplitudes increase significantly with decreasing the Co layer thickness. In this study, the influence of various spin dynamics and static magneto-optical parameters on precession amplitude is examined critically and compared with a previously proposed analytical expression that connects those quantities. It is found that the enhancement of structural-dependent energy transfer efficiency between charge and spin subsystems is indeed responsible for the observed variations in precession amplitudes. On the basis of this fact, we discuss that the spin–orbit interaction that yields perpendicularly spin-polarized electrons in the MLs through the Co/Pd interface is responsible for the observed increase in precession amplitudes of locally excited magnetization. Our approach of employing low-fluence laser excitation of magnetization precession could be practical for developing a non-thermal, all-optical magnetic switching toward photonic memory applications. [ABSTRACT FROM AUTHOR]

We propose an electric measurement technique for the magnetic anisotropy field of ferromagnetic thin films and their tiny patterned structures, particularly, in the case of in-plane magnetic anisotropy. This technique measures the anomalous Hall resistance by sweeping the angle or strength of the external magnetic field. The magnetic anisotropy field can be determined explicitly from the linear dependence of the Hall resistance on the angle and strength of the external magnetic field. The present technique can be applied to both ferromagnetic thin films and their patterned magnetic structures with small volumes, overcoming the signal resolution limit of conventional techniques. [ABSTRACT FROM AUTHOR]

Multiferroic MnTiO3 (MTO) is made up of alternate Mn2+ (3 d 5) and Ti4+ (3 d 0) layers along the c -axis. It undergoes a magnetic spin-flop driven ferroelectric polarization flop beyond ∼ 6 T below T N ∼ 64 K. MTO also exhibits a weak negative thermal expansion along the c -axis below ∼ 90 K. We demonstrate that doping Mn ions at non-magnetic Ti layers acts as a very effective microscopic control parameter to systematically tune both these functional responses. Tuning of c/a lattice parameters in MnTi 1 − x Mn x O3 leads to significant reduction in the spin-flop critical magnetic field from ∼ 6 T to more easily accessible fields (< 2 T for x = 0.05). Simultaneously, the controlled tuning of magnetic frustration due to Mn-doping at Ti sites also helps in a systematic enhancement of anomalous thermal expansion in regard to increasing the onset temperature for anomalous expansion to higher values (by ∼ 40 K for x = 0.10) and also strengthening its magnitude (by ∼ 30 % at 15 K for x = 0.10 in comparison to x = 0.00). Increase in the c/a ratio with Mn doping in MnTiO3 likely causes reduction in the effective magnetocrystalline anisotropy, which leads to a decrease in the value of the spin-flop magnetic field. Detailed temperature-dependent structural analyses shed light on the critical role of exchange striction mechanism in tuning the negative thermal expansion in doped MnTiO3. [ABSTRACT FROM AUTHOR]

An exciting prospect in the field of magnetic fluid hyperthermia (MFH) has been the integration of noble rare earth elements (Eu) with biopolymers (chitosan/dextran) that have optimum structures to tune specific effects on magnetic nanoparticles (NPs). However, the heating efficiency of MNPs is primarily influenced by their magnetization, size distribution, magnetic anisotropy, dipolar interaction, amplitude, and frequency of the applied field, the MNPs with high heating efficiency are still challenging. In this study, a comprehensive experimental analysis has been conducted on single-domain magnetic nanoparticles (SDMNPs) for evaluating effective anisotropy, assessing the impact of particle-intrinsic factors and experimental conditions on self-heating efficiency in both noninteracting and interacting systems, with a particular focus on the dipolar interaction effect. The study successfully reconciles conflicting findings on the interaction effects in the agglomeration and less agglomerated arrangements for MFH applications. The results suggest that effective control of dipolar interactions can be achieved by encapsulating Chitosan/Dextran in the synthesized MNPs. The lower dipolar interactions successfully tune the self-heating efficiency and hold promise as potential candidates for MFH applications. [ABSTRACT FROM AUTHOR]

The quasi-two-dimensional ferromagnet Cr5Te8 is a promising material for spintronic devices due to its near-room-temperature Curie temperature ( T C ), strong magnetic anisotropy, and easily controllable properties. In this study, the anisotropic magnetization of trigonal (T-) Cr5Te8 single crystals is investigated. Our magnetization study reveals that a ferromagnetic transition occurs when the magnetic field is aligned parallel to the c-axis (H / / c), while an antiferromagnetic transition appears for H / / a b , with a strong perpendicular anisotropy in the ground state. However, electron spin resonance (ESR) spectroscopy indicates that the direction of the easy-axis changes from the c-axis to the ab-plane at T V ∼ 190 K as the temperature increases. Furthermore, angle-dependent ESR spectra demonstrate a characteristic of two-dimensional magnetism in the bulk Cr5Te8 single crystal. It is suggested that the temperature-dependent variation in anisotropy is caused by changes in lattice structure through the tuning of the dominant direct-exchange between the intralayers and the super-exchange within the interlayers. The temperature- and field-dependent microwave responses of T-Cr5Te8 are advantageous for the application of this material as a microwave-based spintronic device. [ABSTRACT FROM AUTHOR]

Magnetic tunnel junctions (MTJs) are the core elements of spintronic devices. Now, the mainstream writing operation of MTJs mainly relies on electric current with high energy dissipation, which can be greatly reduced if an electric field is used instead. In this regard, strain-mediated multiferroic heterostructure composed of MTJ and ferroelectrics are promising with the advantages of room temperature and magnetic field-free as already demonstrated by MTJ with in-plane magnetic anisotropy. However, there is no such report on the perpendicular MTJs (p-MTJs), which have been commercialized. Here, we investigate electric-field control of resistance state of MgO-based p-MTJs in multiferroic heterostructures. A remarkable and nonvolatile manipulation of resistance is demonstrated at room temperature without magnetic field assistance. Through various characterizations and micromagnetic simulation, the manipulation mechanism is uncovered. Our work provides an effective avenue for manipulating p-MTJ resistance by electric fields and is notable for high density and ultralow power spintronic devices. [ABSTRACT FROM AUTHOR]

We report a new facile method for the synthesis of prolate cobalt ferrite nanoparticles without additional stabilizers, which involves a co-precipitation reaction of Fe3+ and Co2+ ions in a static magnetic field. The magnetic field is demonstrated to be a key factor for the 1D growth of cobalt ferrite nanocrystals in the synthesis. Transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy are applied to characterize the morphology and structure of the obtained nanoparticles. According to TEM, they represent nanorods with a mean length of 25 nm and a diameter of 3.4 nm that have a monocrystalline structure with characteristic plane spacing of 2.9 Å. XRD and Raman spectroscopy confirm the spinel CoFe2O4 structure of the nanorods. After aging, the synthesized nanorods exhibit maximum saturation magnetization and coercivity equal to 30 emu/g and 0.3 kOe, respectively. Thus, the suggested method is a simple and "green" way to prepare CoFe2O4 nanorods with high aspect ratios and pronounced magnetic properties, which are important for various practical applications, including biomedicine, energy storage, and the preparation of anisotropic magnetic nanocomposites. [ABSTRACT FROM AUTHOR]

The quinary members in the solid solution Hf2Fe1−δRu5−xIrx+δB2 (x=1–4, VE=63–66) have been investigated experimentally and computationally. They were synthesized via arc‐melting and analyzed by EDX and X‐ray diffraction. Density functional theory (DFT) calculations predicted a preference for magnetic ordering in all members, but with a strong competition between ferro‐ and antiferromagnetism arising from interchain Fe−Fe interactions. The spin exchange and magnetic anisotropy energies predicted the lowest magnetic hardness for x=1 and 3 and the highest for x=2. Magnetization measurements confirm the DFT predictions and demonstrate that the antiferromagnetic ordering (TN=55–70 K) found at low magnetic fields changed to ferromagnetic (TC=150–750 K) at higher fields, suggesting metamagnetic behavior for all samples. As predicted, Hf2FeRu3Ir2B2 has the highest intrinsic coercivity (Hc=74 kA/m) reported to date for Ti3Co5B2‐type phases. Furthermore, all coercivities outperform that of ferromagnetic Hf2FeIr5B2, indicating the importance of AFM interactions in enhancing magnetic anisotropy in these materials. Importantly, two members (x=1 and 4) maintain intrinsic coercivities in the semi‐hard range at room temperature. This study opens an avenue for controlling magnetic hardness by modulating antagonistic AFM and FM interactions in low‐dimensional rare‐earth‐free magnetic materials. [ABSTRACT FROM AUTHOR]

Electric field controlled magnetic devices have attracted interest in the area of magnetic recording research, owing to their lower power consumption and high stability. While heterostructures composed of Co and carbon materials exhibit unique properties, our understanding of the magnetic properties of Co on graphene with a wavelike structure and related electric field-controlled phenomena remains limited. Here, we demonstrate the preparation of a customized Co/graphene structure, in which the controllability of the coercive force is enhanced. Taking the coercive force and geometric factor of Co into consideration, a shape-dependent magnetic anisotropy is proposed, which sufficiently explains the correlation between the coercive force and the aspect ratios of the Co stripes. For the magnetic field perpendicular to the bottom lines of canyons, the adjustment capability of the coercive force is enhanced under conditions of a more negatively charged surface. Based on the large electric field and related magnetic anisotropy energy, a ferro-ionic control (FeIC) model is proposed, which describes the relationship between the electric potential and coercive force in electrified conditions. Based on a FeIC model with a preferred orientation, we propose a design of an integrated FeIC inductor with field tunability that could strongly impact the field of integrated-circuit design, resulting in wider applications and functionalities of chips. [ABSTRACT FROM AUTHOR]

Magnonics has long been hailed as a promising technology poised to overcome the heat dissipation challenges in traditional electronic devices. With the escalating integration level of magnon devices, the demand arises for lower external field excitation conditions, coupled with enhanced coherence and frequency-selective excitation characteristics. In this proposal, we suggest introducing a localized perpendicular magnetic anisotropy nanofilm stack into the spin-wave transmission channel to finely regulate the propagation characteristics of spin waves. This adjustment can be achieved by altering the width and period of the stack in both horizontal and vertical dimensions. Additionally, the optimal transmission characteristics of spin waves are achieved at low frequencies (1–1.67 GHz) and in the presence of small magnetic fields (0–20 mT). Frequency-selective spin waves with triggering stability can effectively prevent signal folding resulting from changes in microwave power within the range of −30 to 0 dBm. At 1.08 GHz, the group velocity of frequency-selective spin waves can be increased by up to 2.86 times. This innovative method of regulating spin waves presents a potential alternative pathway for the development of future magnonic circuits. [ABSTRACT FROM AUTHOR]

We investigate the magnetic properties of La2/3Sr1/3MnO3 (LSMO) membranes released from an SrTiO3 (STO) substrate by selectively etching an Sr4Al2O7 sacrificial buffer layer. The magnetic moment and Curie temperatures (TC) of the released LSMO membranes improve significantly over their substrate-bound counterparts. We attribute these enhancements to suppressing strain and oxygen octahedral rotations that are present in substrate-bound films. Moreover, comparing the magnetic hysteresis loops obtained with magnetic fields applied along several crystallographic orientations demonstrates enhanced (weakened) perpendicular (in-plane) magnetic anisotropy in the released LSMO membranes. Our results contribute to potential applications of released LSMO membranes toward flexible spintronics devices, where high spin polarization and TC are desired. [ABSTRACT FROM AUTHOR]

Magnetars are a type of pulsars powered by magnetic field energy. Part of the X‐ray luminosities of magnetars in quiescence have a thermal origin and can be fitted by a blackbody spectrum with the surface temperature, much higher than the typical values for rotation‐powered pulsars. The persistent thermal emissions and bursts of magnetars indicate the presence of some internal heat sources in their outer crusts. In this work, we have formulated the energy balance equation and applied it to investigate the thermal evolution in the magnetar crust, taking into account the heating mechanisms of Ohmic decay and electron capture processes. This model can explain the changes in the X‐ray luminosity of the magnetars. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the impact of an external magnetic field on the Weibel instability driven by temperature anisotropy in a magnetized plasma. The study provides the influence of electron temperature anisotropy, considering both cold as well as warm ions. We derive expressions for the growth rate Γ (s−1) in each case to quantify the effect of some specific parameters on the instability. For example, the growth rate is plotted against the magnetic field for three distinct cases: considering only electrons, including cold ions, and incorporating warm ions. It is observed that the growth rate decreases as the applied magnetic field increases. Furthermore, the addition of both cold and warm ions to the plasma significantly influences the observed effects. It can be explained as follows: in the presence of cold ions, the growth rate is decreased with an increase in the wave number kz (cm−1). In addition, a decrease in the growth rate is observed with an increasing wave number in the case of warm ions. Therefore, it can be seen that the Weibel instability, propelled by thermal anisotropy, holds significant implications owing to its prevalence in both astrophysical and laboratory plasmas. The findings presented here are expected to contribute to the advancements in magnetic field generation and particle acceleration in various astrophysical phenomena, including gamma-ray bursts, relativistic collisionless shock fronts, radio supernovae, and pulsar winds. [ABSTRACT FROM AUTHOR]

Magnetic Field Assisted Additive Manufacturing (MFAAM), 3D printing in a magnetic field, has the potential to fabricate high magnetic strength anisotropic bonded magnets. Here, 10, 35, and 54 wt% strontium ferrite bonded magnets using polyamide 12 binder were developed by twin screw compounding process and then printed via MFAAM samples in zero, and in 0.5 Tesla (H parallel to the print direction and print bed). The hysteresis curves were measured using a MicroSense EZ9 Vibrating Sample Magnetometer (VSM) for 3 different mount orientations of the sample on the sample holder to explore the magnetic anisotropy. The samples printed in zero field exhibited a weak anisotropy with an easy axis perpendicular to the print direction. This anisotropy is caused by the effect of shear flow on the orientation of the magnetic platelets in the 3D printer head. For the MFAAM samples, the S values are largest along the print bed normal. This anisotropy is caused by the field. The alignment of the magnetic particles happens when the molten suspension is in the extruder. When the material is printed, it is folded over on the print bed and its easy axis rotates 90° parallel to the print bed normally. Little realignment of the particles happens after it is printed, suggesting a sharp drop in temperature once the composite touches the print bed, indicating that field-induced effects in the nozzle dominate the anisotropy of MFAAM deposited samples. [ABSTRACT FROM AUTHOR]

In this study, we investigate the potential of heavy quarkonia within a magnetized hot QGP medium having finite momentum anisotropy. The phenomenon of inverse magnetic catalysis is introduced into the system, influencing the magnetic field-modified Debye mass and thereby altering the effective quark masses. Concurrently, the impact of momentum anisotropy in the medium is considered that influence the particle distribution in the medium. The thermal decay width and dissociation temperature of quarkonium states, specifically the 1S and 2S states of charmonium and bottomonium, are computed. Our results reveal that both momentum anisotropy and the inverse magnetic catalysis effects play a significant role in modifying the thermal decay width and dissociation temperature of these heavy quarkonia states. [ABSTRACT FROM AUTHOR]

The application of a magnetic field perpendicular to the surface of a graphene cantilever generates a bending force owing to the strong anisotropy of the magnetic susceptibility. We calculate the mechanically stable equilibrium shape of a graphene cantilever in the presence of a magnetic field by minimizing the magnetic and bending energies, which are calculated using the tight-binding model and the Tersoff–Brenner potential, respectively. Furthermore, the introduction of a continuous model enables the size-dependence of the displacement by bending to be considered. [ABSTRACT FROM AUTHOR]

We have investigated the effect of an external electric field on the magnetic properties of Co2MnAl thin films deposited on a lead magnesium niobate-lead titanate (PMN-PT) (011) substrate. Stain-induced magnetoelectric coupling affects the magnetic properties of the Co2MnAl/PMN-PT system. The piezo-strain induced by applying an external field normal to the surface induces only in-plane strain, which leads to the rotation of easy-axis orientation of Co2MnAl from [100] to [ 01 1 ¯ ] direction. The remanent magnetization states and coercivity of the Co2MnAl film vary significantly and asymmetrically with the applied voltage due to anisotropic strain originating from PMN-PT. Electrical control of magnetic anisotropy in a Co2MnAl Heusler compound at room temperature will be of interest for realizing next-generation magnetoelectric random access memory devices. [ABSTRACT FROM AUTHOR]

We studied the influence of the superconducting state on the magnetic properties in a thick IrMn(100 nm)/NiFe(100 nm) bilayer deposited by magnetron sputtering onto an yttrium–barium–copper–oxide (YBCO) substrate that was previously synthesized by the acetate method. The results from magnetization experiments showed that the sign of the effective exchange fields switched from positive, in the as-prepared heterostructure, to negative values when the sample goes below the superconducting temperature of the YBCO substrate. We, thus, demonstrated that the YBCO substrate, in its superconducting state, strongly influences the magnetic anisotropy of the thick ferromagnetic NiFe layer due to the proximity effect that occurs at the YBCO–NiFe interface, where a non-collinear magnetic spin structure is formed during the in-field sample deposition. [ABSTRACT FROM AUTHOR]

The advent of van der Waals (vdW) ferromagnetic (FM) and antiferromagnetic (AFM) materials offers unprecedented opportunities for spintronics and magneto‐optic devices. Combining magnetic Kerr microscopy and density functional theory calculations, the AFM‐FM transition is investigated and a surprising abnormal magneto‐optic anisotropy in vdW CrSBr associated with different magnetic phases (FM, AFM, or paramagnetic state) is discovered. This unique magneto‐optic property leads to different anisotropic optical reflectivity from different magnetic states, permitting direct imaging of the AFM Néel vector orientation and the dynamic process of the AFM‐FM transition within a magnetic field. Using Kerr microscopy, not only the domain nucleation and propagation process is imaged but also the intermediate spin‐flop state in the AFM‐FM transition is identified. The unique magneto‐optic property and clear identification of the dynamics process of the AFM‐FM phase transition in CrSBr demonstrate the promise of vdW magnetic materials for future spintronic technology. [ABSTRACT FROM AUTHOR]

The precise control of magnetic properties at the microscale has transformative potential in healthcare and human‐robot interaction. This research focuses on understanding the magnetic interactions in nanostructure assemblies responsible for microactuation. By combining experimental measurements and micromagnetic simulations, the interactions in both nanocube and nanochain assemblies are elucidated. Hysteresis measurements and first‐order reversal curves (FORC) reveal that the spatial arrangement of these assemblies governs their collective magnetism. A critical concentration threshold is observed where a transition from ferromagnetic‐like to antiferromagnetic‐like coupling occurs. Leveraging the high uniaxial anisotropy of 1D nanochains, the remanent magnetization of assembled chain structures is maximized for efficient magneto‐mechanical energy transduction. By utilizing an optimized magnetic nanostructure concentration, a flexible film is fabricated, and its significantly enhanced mechanical deformation response to a small magnetic field, surpassing conventional particle‐based samples by a factor of five, is demonstrated. Demonstrating excellent transduction efficiency, visible deformations such as bending and S‐shaped twisting modes are achieved with an applied field of less than 400 Oe. Furthermore, the reprogrammability of the actuator, achieving a U‐shaped bending mode by altering its magnetization profile, is showcased. This research provides valuable insights for designing reconfigurable and effective microactuators and devices at significantly smaller scales than previously possible. [ABSTRACT FROM AUTHOR]

Films with perpendicular magnetic anisotropy have obvious storage performance advantages, so being able to easily change the direction of magnetization of a Y3Fe5O12 (YIG) film is an important aim in the field of photo-magnetic storage. A series of Bi,Mn co-doped Y3Fe5O12 films with good crystallinity and great magneto-optical properties, were prepared via the liquid phase epitaxial method. These films are pseudomorphic structures in the substrate and have high perpendicular magnetic anisotropy. By comparing the change in the calculated magnetic anisotropy and the actual magnetic anisotropy, with Mn3+ content, we see that: the stress-induced magnetic anisotropy increases with the increase of lattice mismatch; on the other hand, with increasing Mn3+ content, the magnetostriction effect decreases first and then increases, which reflects the regulation effect of Mn3+ and lattice mismatch on the perpendicular magnetic anisotropy. Finally, the magnetic anisotropy field (>3000 Oe) is higher than that of Mn:YIG (<1000 Oe) as previously reported. [ABSTRACT FROM AUTHOR]

In this paper, we introduce a design concept for a spin-torque nano-oscillator capable of generating spin-wave (SW) packets using magnetic droplets tuned by an electric field (E-field). A comparison is made between this device concept and a conventional setup, where SWs are generated by an oscillating external magnetic field, revealing similar results. The design incorporates a CoFeB layer with perpendicular magnetic anisotropy, acting as a waveguide for propagating SW packets. Adjusting the pulse width of applied E-fields leads to observable changes in the amplitude and periodicity of SW packets. Additionally, this study explores the potential of encoding SW packets as binary signals ("0" and "1"). The findings offer valuable insights into the applications of magnetic droplets and electric-field tuning for spin-wave packet generation, with potential implications for various spintronic devices and technologies. [ABSTRACT FROM AUTHOR]

Anchoringsingle-molecule magnets (SMMs) on the surface of nanostructures is gaining particular interest in the field of molecular magnetism. The accurate organization of SMMs on low-dimensional substrates enables controlled interactions and the possibility of individual molecules' manipulation, paving the route for a broad range of nanotechnological applications. In this comprehensive review article, the most studied types of SMMs are presented, and the quantum-mechanical origin of their magnetic behavior is described. The nanostructured matrices were grouped and characterized to outline to the reader their relevance for subsequent compounding with SMMs. Particular attention was paid to the fact that this process must be carried out in such a way as to preserve the initial functionality and properties of the molecules. Therefore, the work also includes a discussion of issues concerning both the methods of synthesis of the systems in question as well as advanced measurement techniques of the resulting complexes. A great deal of attention was also focused on the issue of surface–molecule interaction, which can affect the magnetic properties of SMMs, causing molecular crystal field distortion or magnetic anisotropy modification, which affects quantum tunneling or magnetic hysteresis, respectively. In our opinion, the analysis of the literature carried out in this way will greatly help the reader to design SMM-nanostructure systems. [ABSTRACT FROM AUTHOR]

Unidirectional magnetic anisotropy induced by exchange bias (EB) between ferromagnetic and antiferromagnetic layers is of paramount importance in various spintronic devices. Traditional setting and optimization of EB involve cooling through the Néel temperature of the antiferromagnets under biasing field in vacuum furnace which takes hours of time and cannot realize localized control of EB. Herein, an alternative process to configure EB by injection of microsecond current impulse for locally heating of the heterostructure is reported. 180‐degree exchange bias switching has been realized in both anisotropic magnetoresistance and giant magnetoresistance units, resulting in tunable magnetic field sensing functionalities. This mechanism for pinpoint control of EB provides more freedom for the design and optimization of various sensing and logic spintronics. [ABSTRACT FROM AUTHOR]

The magnetic properties and the existence of spin reorientation have been systematically investigated in MnNiGa ribbons. The thermomagnetic curve reveals that as-spun and annealed ribbons undergo a two-step magnetic structural transformation and the magnetic properties of the annealed ribbons are improved. The splitting behaviour of zero-field-cooled and filed-cooled (ZFC-FC) curve shows that the ribbon has occurred a spin reorientation transformation. The ZFC and isothermal magnetization curves tested by changing the direction of the magnetic field illustrate the existence of magnetic anisotropy, and the direction of H// is easily magnetized. In the direction of easy magnetization, the value of magnetic entropy is about 1.54 J/kg K. The easy magnetization direction is proved to be in-plane by the decrease of the magnetic domain phase shift. It is clear that the magnetoresistance is negative in all temperature ranges and the nonlinear variation at low fields accounts for the presence of spin reorientation. The variation of Hall resistance curve in a low magnetic field reflects the existence of an abnormal Hall effect. [ABSTRACT FROM AUTHOR]

We use the TNG50 cosmological magnetohydrodynamical simulation of the IllustrisTNG project to show that magnetic fields in the circumgalactic medium (CGM) have significant angular structure. This azimuthal anisotropy at fixed distance is driven by galactic feedback processes that launch strong outflows into the halo, preferentially along the minor axes of galaxies. These feedback-driven outflows entrain strong magnetic fields from the interstellar medium, dragging fields originally amplified by small-scale dynamos into the CGM. At the virial radius, z  = 0 galaxies with M⋆ ∼  |$10^{10}\, \rm {M_\odot }$| show the strongest anisotropy (∼0.35 dex). This signal weakens with decreasing impact parameter, and is also present but weaker for lower mass as well as higher mass galaxies. Creating mock Faraday rotation measure (RM) sightlines through the simulated volume, we find that the angular RM trend is qualitatively consistent with recent observational measurements. We show that rich structure is present in the circumgalactic magnetic fields of galaxies. However, TNG50 predicts small RM amplitudes in the CGM that make detection difficult as a result of other contributions along the line of sight. [ABSTRACT FROM AUTHOR]

The magnetoelectric effect (ME) is an important strain mediated-phenomenon in a ferromagnetic-piezoelectric composite for a variety of sensors and signal processing devices. A bias magnetic field, in general, is essential to realize a strong ME coupling in most composites. Magnetic phases with (i) high magnetostriction for strong piezomagnetic coupling and (ii) large anisotropy field that acts as a built-in bias field are preferred so that miniature, ME composite-based devices can operate without the need for an external magnetic field. We are able to realize such a magnetic phase with a composite of (i) barium hexaferrite (BaM) with high magnetocrystalline anisotropy field and (ii) nickel ferrite (NFO) with high magnetostriction. The BNx composites, with (100 − x) wt.% of BaM and x wt.% NFO, for x = 0–100, were prepared. X-ray diffraction analysis shows that the composites did not contain any impurity phases. Scanning electron microscopy images revealed that, with an increase in NFO content, hexagonal BaM grains become prominent, leading to a large anisotropy field. The room temperature saturation magnetization showed a general increase with increasing BaM content in the composites. NFO rich composites with x ≥ 60 were found to have a large magnetostriction value of around −23 ppm, comparable to pure NFO. The anisotropy field HA of the composites, determined from magnetization and ferromagnetic resonance (FMR) measurements, increased with increasing NFO content and reached a maximum of 7.77 kOe for x = 75. The BNx composite was cut into rectangular platelets and bonded with PZT to form the bilayers. ME voltage coefficient (MEVC) measurements at low frequencies and at mechanical resonance showed strong coupling at zero bias for samples with x ≥ 33. This large in-plane HA acted as a built-in field for strong ME effects under zero external bias in the bilayers. The highest zero-bias MEVC of ~22 mV/cm Oe was obtained for BN75-PZT bilayers wherein BN75 also has the highest HA. The Bilayer of BN95-PZT showed a maximum MEVC ~992 mV/cm Oe at electromechanical resonance at 59 kHz. The use of hexaferrite–spinel ferrite composite to achieve strong zero-bias ME coupling in bilayers with PZT is significant for applications related to energy harvesting, sensors, and high frequency devices. [ABSTRACT FROM AUTHOR]

Employing short laser pulses with a duration below 100 fs for changing magnetic state of magnetically-ordered media has developed into a distinct branch of magnetism femtomagnetism which aims at controlling magnetization at ultimately short timescales. Among plethora of femtomagnetic phenomena, there is a class related to impact of femtosecond pulses on magnetic anisotropy of materials and nanostructures which defines orientation of magnetization, magnetic resonance frequencies and spin waves propagation. We present a review of main experimental results obtained in this field. We consider basic mechanisms responsible for a laser-induced change of various anisotropy types: magnetocrystalline, magnetoelastic, interfacial, shape anisotropy, and discuss specifics of these processes in magnetic metals and dielectrics. We consider several examples and describe features of magnetic anisotropy changes resulting from ultrafast laser-induced heating, impact of laser-induced dynamic and quasistatic strains and resonant excitation of electronic states. We also discuss perspectives of employing various mechanisms of laser-induced magnetic anisotropy change for enabling processes prospective for developing devices. We consider precessional magnetization switching for opto-magnetic information recording, generation of high-frequency strongly localized magnetic excitations and fields for magnetic nanotomography and hybrid magnonics, as well as controlling spin waves propagation for optically-reconfigurable magnonics. We further discuss opportunities which open up in studies of ultrafast magnetic anisotropy changes because of using short laser pulses in infrared and terahertz ranges. [ABSTRACT FROM AUTHOR]