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We derive four reduced two-dimensional models that describe, at different spatial scales, the micromagnetics of ultrathin ferromagnetic materials of finite spatial extent featuring perpendicular magnetic anisotropy and interfacial Dzyaloshinskii–Moriya interaction. Starting with a microscopic model that regularizes the stray field near the material's lateral edges, we carry out an asymptotic analysis of the energy by means of Γ -convergence. Depending on the scaling assumptions on the size of the material domain versus the strength of dipolar interaction, we obtain a hierarchy of the limit energies that exhibit progressively stronger stray field effects of the material edges. These limit energies feature, respectively, a renormalization of the out-of-plane anisotropy, an additional local boundary penalty term forcing out-of-plane alignment of the magnetization at the edge, a pinned magnetization at the edge, and, finally, a pinned magnetization and an additional field-like term that blows up at the edge, as the sample's lateral size is increased. The pinning of the magnetization at the edge restores the topological protection and enables the existence of magnetic skyrmions in bounded samples. [ABSTRACT FROM AUTHOR]

The interplay of lattice, electronic, and spin degrees of freedom at epitaxial complex oxide interfaces provides a route to tune their magnetic ground states. Unraveling the competing contributions is critical for tuning their functional properties. The relationship between magnetic ordering and magnetic anisotropy and the lattice symmetry, oxygen content, and film thickness in compressively strained LaMnO3 (LMO)/LaCrO3 (LCO) superlattices is investigated. Mn–O–Cr antiferromagnetic superexchange interactions across the heterointerface result in a net ferrimagnetic magnetic structure. Bulk magnetometry measurements reveal isotropic in‐plane magnetism for as‐grown oxygen‐deficient thin samples due to equal fractions of orthorhombic a+a‐c‐, and a‐a+c‐ twin domains. As the superlattice thickness is increased, in‐plane magnetic anisotropy emerges as the fraction of the a+a‐c‐ domain increases. On annealing in oxygen, the suppression of oxygen vacancies results in a contraction of the lattice volume, and an orthorhombic to rhombohedral transition leads to isotropic magnetism independent of the film thickness. The complex interactions are investigated using high‐resolution synchrotron diffraction and X‐ray absorption spectroscopy. These results highlight the role of the evolution of structural domains with film thickness, interfacial spin interactions, and oxygen‐vacancy‐induced structural phase transitions in tuning the magnetic properties of complex oxide heterostructures. [ABSTRACT FROM AUTHOR]

Study of the domain wall (DW) dynamics in ultrathin films with perpendicular magnetic anisotropy (PMA) opens the way to envisage the low-power and high-performance memory and logic devices. Here, we have studied the magnetization reversal and DW dynamics of Pt/Co/Pt ultrathin films having PMA. The Pt/Co/Pt ultrathin trilayers have been fabricated using molecular beam epitaxy (MBE) at room temperature. The DW velocity measurements were performed by bubble domain expansion method with an additional homemade coil in order to apply out-of-plane (OOP) field in the polar magneto-optic Kerr effect (P-MOKE)-based microscope. The DW motion is limited only in creep regime, and the maximum observed DW velocity is 32 mm/s. Further, it has been shown that the DW velocity can be enhanced via increasing Co thickness. [ABSTRACT FROM AUTHOR]

The precise manipulation of perpendicular magnetic anisotropy (PMA) and near-infrared plasmonic states holds immense significance for advanced nanoscale spintronics devices including magnetic random-access memory and epsilon-near-zero (ENZ) photonic devices. Notwithstanding the inherent tendency of oxide thin films to favor an in-plane magnetic easy axis, our study unveils an innovative approach to exert experimental control over magnetic anisotropy, magnetic phase in SrRuO3 (SRO) films by growing them coherently and controlling at nanoscale levels via reflection high-energy electron diffraction (RHEED)-assisted pulsed laser deposition (PLD) on distinctively orientedspecifically, (001), (011), and (111) SrTiO3 (STO) single crystalline substrates. Our comprehensive magnetic measurements unequivocally confirm a clear dependence on magnetic anisotropy with more than one competing magnetic phase with different coercivity and saturation magnetization. A larger perpendicular magnetic anisotropy (PMA) is observed for coherently strained SRO films on (001)-oriented STO compared to their counterparts on (011) and (111)-oriented STO. On the other hand, the orientation-dependent SRO films exhibit tunable plasmonic ENZ, increased metallicity, flexible optical conductivity, and customizable optical transparency in the near-infrared region. These results not only provide a straightforward and effective pathway for achieving tunable PMA and transparent plasmonic states in epitaxial oxide layers but also hold the potential to develop state-of-the-art oxide-based optospin–orbit coupled spintronic switching and memory devices. [ABSTRACT FROM AUTHOR]

Postsynthetic, position‐selective addition of properties to materials constitutes a paradigm shifting step in materials engineering. The approach enables creation of material systems inaccessible by equilibrium and near‐equilibrium synthesis and can be applied in novel practical applications as well as fundamental physics studies over a range of length and energy scales. Ion implantation is a versatile, scalable, industry‐compatible tool, enabling the next step in this development. Herein, ion implantation is used to design and functionalize a mesoscopic magnetic architecture. A self‐supporting mask is combined with implantation of 60 keV Fe ions to create an embedded array of ≈8 μm‐wide circular ferromagnetic regions in a Pd film. The approach is contactless, free from surface residues, and requires no focusing or scanning of the beam. Magnetic properties of the array are probed with longitudinal magneto‐optic Kerr effect measurement while varying sample temperature and applied magnetic field. Microstructures are visualized with Kerr microscopy and compared to the Fe distribution measured with microbeam proton‐induced X‐Ray emission. Sample topography after implantation is obtained by atomic force microscopy, while ion beam analysis is used to probe concentration depth profiles of implanted Fe, impurities, and to investigate material mixing. [ABSTRACT FROM AUTHOR]

Abstract: The different magnetic behaviors of LaCoO$$_3$$ 3 films grown on LaAlO$$_3$$ 3 and SrTiO$$_3$$ 3 substrates are related to the Co–O–Co bond angles and the constraints imposed on the Co–O bond lengths by the substrate geometries. The observed magnetic behavior is not consistent with ferromagnetism. Rather, long-range antiferromagnetic order occurs below $$T \approx 90$$ T ≈ 90  K when the Co–O–Co bond angle is greater than 163$$^\circ$$ ∘ , consistent with the behavior of bulk and nanoparticles forms of LaCoO$$_3$$ 3 . A LaAlO$$_3$$ 3 substrate prevents magnetic long-range order at low temperatures near the film–substrate interface and collinear antiferromagnetic sublattices away from the interface. At low temperatures, the antiferromagnetically ordered sublattices are non-collinear in films grown on SrTiO$$_3$$ 3 substrates, leading to a significant net moment. The net moment is controlled by the geometry imposed by the substrate upon which the LaCO$$_3$$ 3 film is grown. Graphical abstract

Magnonics is an emerging field within spintronics that focuses on developing novel magnetic devices capable of manipulating information through the modification of spin waves in nanostructures with submicron size. Here, we provide a confined magnetic rectangular element to modulate the standing spin waves, by changing the saturation magnetisation (MS), exchange constant (A), and the aspect ratio of rectangular magnetic elements via micromagnetic simulation. It is found that the bulk mode and the edge mode of the magnetic element form a hybrid with each other. With the decrease in MS, both the Kittel mode and the standing spin waves undergo a shift towards higher frequencies. On the contrary, as A decreases, the frequencies of standing spin waves become smaller, while the Kittel mode is almost unaffected. Moreover, when the length-to-width aspect ratio of the element is increased, standing spin waves along the width and length become split, leading to the observation of additional modes in the magnetic spectra. For each mode, the vibration style is discussed. These spin dynamic modes were further confirmed via FMR experiments, which agree well with the simulation results. [ABSTRACT FROM AUTHOR]

Abstract The interplay of lattice, electronic, and spin degrees of freedom at epitaxial complex oxide interfaces provides a route to tune their magnetic ground states. Unraveling the competing contributions is critical for tuning their functional properties. The relationship between magnetic ordering and magnetic anisotropy and the lattice symmetry, oxygen content, and film thickness in compressively strained LaMnO3 (LMO)/LaCrO3 (LCO) superlattices is investigated. Mn–O–Cr antiferromagnetic superexchange interactions across the heterointerface result in a net ferrimagnetic magnetic structure. Bulk magnetometry measurements reveal isotropic in‐plane magnetism for as‐grown oxygen‐deficient thin samples due to equal fractions of orthorhombic a+a‐c‐, and a‐a+c‐ twin domains. As the superlattice thickness is increased, in‐plane magnetic anisotropy emerges as the fraction of the a+a‐c‐ domain increases. On annealing in oxygen, the suppression of oxygen vacancies results in a contraction of the lattice volume, and an orthorhombic to rhombohedral transition leads to isotropic magnetism independent of the film thickness. The complex interactions are investigated using high‐resolution synchrotron diffraction and X‐ray absorption spectroscopy. These results highlight the role of the evolution of structural domains with film thickness, interfacial spin interactions, and oxygen‐vacancy‐induced structural phase transitions in tuning the magnetic properties of complex oxide heterostructures.

Oxygen coordination and vacancy ordering play an important role in dictating the functionality of complex oxides. In this work, an unconventional layering of oxygen ions in a mixed conductor SrCo1-xFexO3-δ (SCFO) thin film grown epitaxially on SrTiO3 (STO) is reported. Scanning transmission electron microscopy (STEM) reveals alternating layers of oxygen deficiency along the growth direction, with the oxygen-rich layer correlated with the neighboring Co,Fe-site intensity, and contraction of the Sr–Sr distance. Density functional theory (DFT) calculations and STEM image simulations support the emergence of periodic (Co,Fe)O6 and (Co,Fe)O4/(Co,Fe)O5 layers, an ordering that is also sensitive to the Co:Fe ratio. [ABSTRACT FROM AUTHOR]

The effect of oxygen reduction on the magnetic properties of LaFeO3−δ (LFO) thin films was studied to better understand the viability of LFO as a candidate for magnetoionic memory. Differences in the amount of oxygen lost by LFO and its magnetic behavior were observed in nominally identical LFO films grown on substrates prepared using different common methods. In an LFO film grown on as-received SrTiO3 (STO) substrate, the original perovskite film structure was preserved following reduction, and remnant magnetization was only seen at low temperatures. In a LFO film grown on annealed STO, the LFO lost significantly more oxygen and the microstructure decomposed into La- and Fe-rich regions with remnant magnetization that persisted up to room temperature. These results demonstrate an ability to access multiple, distinct magnetic states via oxygen reduction in the same starting material and suggest LFO may be a suitable materials platform for nonvolatile multistate memory. [ABSTRACT FROM AUTHOR]

Magnetic skyrmions have emerged as promising elements for encoding information toward biomimetic computing applications due to their pseudoparticle nature and efficient coupling to spin currents. A key hindrance for skyrmionic devices is their instability against elongation at zero magnetic field (ZF). Prevailing materials approaches focused on tailoring skyrmion energetics have found ZF configurations to be highly sensitive, which imposes significant growth constraints and limits their device scalability. This work demonstrates that designer ZF skyrmion configurations can be robustly stabilized within chiral multilayer stacks by exploiting a duet of interlayer exchange couplings (IECs). Microscopic imaging experiments show that varying the two IECs enables the coarse and fine‐tuning of ZF skyrmion stability and density. Micromagnetic simulations reveal that the duo‐IEC approach is distinguished by its influence on the kinetics of skyrmion nucleation, in addition to the ability to tailor energetics, resulting in a substantially expanded parameter space, and enhanced stability for individual ZF skyrmions. This study underscores the importance of IEC as a means of stabilizing and controlling ZF skyrmions, paving the way to scalable skyrmion‐based devices. [ABSTRACT FROM AUTHOR]

The use of a complex ferromagnetic system to manipulate GHz surface acoustic waves (SAWs) is a rich current topic under investigation, but the high‐power nonlinear regime is under‐explored. Focused SAWs are introduced, which provide a way to access this regime with modest equipment. The symmetry of the magneto‐acoustic interaction can be tuned by interdigitated transducer design which can introduce additional strain components. Here, the impact of focused acoustic waves versus standard unidirectional acoustic waves in significantly enhancing the magnon‐phonon coupling behavior is compared. Analytical simulation results based on the modified Landau–Lifshitz–Gilbert theory show good agreement with experimental findings. Nonlinear input power dependence of the transmission through the device is also reported. This experimental observation is supported by the micromagnetic simulation using mumax3 to model the nonlinear dependence. These results pave the way for extending the understanding and design of acoustic wave devices for the exploration of acoustically driven spin wave resonance physics. [ABSTRACT FROM AUTHOR]

Domain wall (DW) statics and dynamics have been immensely studied for the last few decades in a disordered medium due to rich fundamental physics and spintronics applications. Here, we have studied the DW dynamics in Pt/CoFeB/MgO thin film with perpendicular magnetic anisotropy. We have observed an unusual behaviour in the DW dynamics which cannot be only explained via universal creep or depinning law. At low driving force, the sample follows the universal creep law; however, near the depinning field ( H d ), an excess velocity has been observed in DW dynamics in comparison to the usual creep law. We propose that, due to additional relaxation events near H d , the DW propagation length is increased and hence the DW velocity. The excess velocity has been modelled to a modified creep law. [ABSTRACT FROM AUTHOR]

The magnetic properties of ferromagnetic thin films with three spin layers were investigated using fourth order perturbed Heisenberg Hamiltonian with all seven magnetic energy parameters for simple cubic lattice. Total Magnetic energy was formulated in terms of spin exchange interaction, second order and fourth order anisotropy, in plane and out plane applied magnetic fields, demagnetization energy and stress induced anisotropy in three spin layers. 3D plot of total magnetic energy versus angle and stress induced anisotropy were plotted for the different values of second order magnetic anisotropy constants. All other magnetic energy parameters were kept at constant values. All the peaks are closely packed in the graphs plotted using fourth order perturbed Heisenberg Hamiltonian compared to peaks in the graphs plotted using second and third order perturbed Heisenberg Hamiltonian. The order of magnetic energy changed when the values of second order anisotropy constants of three spin layers are varied. The order of magnetic energy is higher, when the second order magnetic anisotropy constant in the top spin layer is less than those of the bottom and middle spin layers. The order of magnetic energy is lower, when the second order magnetic anisotropy constant in the bottom spin layer is less than those of the top and middle spin layers. In addition, the angle between consecutive magnetic easy and hard direction is nearly 90 degrees for all the cases.

Abstract The use of a complex ferromagnetic system to manipulate GHz surface acoustic waves (SAWs) is a rich current topic under investigation, but the high‐power nonlinear regime is under‐explored. Focused SAWs are introduced, which provide a way to access this regime with modest equipment. The symmetry of the magneto‐acoustic interaction can be tuned by interdigitated transducer design which can introduce additional strain components. Here, the impact of focused acoustic waves versus standard unidirectional acoustic waves in significantly enhancing the magnon‐phonon coupling behavior is compared. Analytical simulation results based on the modified Landau–Lifshitz–Gilbert theory show good agreement with experimental findings. Nonlinear input power dependence of the transmission through the device is also reported. This experimental observation is supported by the micromagnetic simulation using mumax3 to model the nonlinear dependence. These results pave the way for extending the understanding and design of acoustic wave devices for the exploration of acoustically driven spin wave resonance physics.

Magnetron sputtering is a very versatile technique extensively employed for the deposition/growth of thin films. However, the deposition of desirable magnetic films is one of the challenges confronting magnetron sputtering owing to the shunting of magnetic flux by magnetic targets in conventional magnetron sputtering equipment. This flux shunting culminates in lower plasma density, non-uniform plasma confinement, and uneven erosion of magnetic targets, adversely affecting the growing films' thickness uniformity and chemical homogeneity—the latter can be particularly serious in magnetron co-sputtering. In this article, it is discussed that these issues can be avoided by cylindrical sputtering. As for planar sputtering, formerly offered technical solutions including the utilization of thin foils as magnetic targets, the deployment of gapped targets somewhat allowing the magnetic flux of the magnetron assembly, the employment of a target heating system increasing a magnetic target's temperature greater than or equal to its Curie temperature, facing target sputtering, magnetron sputtering assisted by coupled plasma inductively generated in an internal coil, and the generation of plasma remotely from magnetic targets (i.e., high target utilization sputtering) are scrutinized with their advantages/disadvantages being further examined. Finally, it is discussed that not only can auxiliary grid deployment mitigate/remove the issues of planar magnetron sputtering by modifying spatial plasma density distribution near the target but also it can solely shoulder the responsibility of ionization enhancement and plasma confinement for deposition of magnetic films. [ABSTRACT FROM AUTHOR]

Controlled transport of biological cells in biomedical applications such as sorting, cell sequencing, and assembly of multicellular structures is a technological challenge. Research areas such as drug delivery or tissue engineering can benefit from precise cell location resulting in faster response rates or more complex tissue structures. Using computational methods, different soft magnetic elements with curved edges are designed to form a transport network, enabling transport and all functionalities for the manipulation of microbeads and cells on surfaces by rotational magnetic fields. Building blocks with bimodal functionalities due to segments of differently curved edges permit breakpoints as well as switchable transport via splitting and combining elements. Connecting the elements, networked paths are realized which allow variable movement patterns of magnetic carriers and cells. The direction of magnetic field rotation is altered to direct the beads and cells into different transport lines, and the exact timing is not critical. The networks are used to achieve deterministic movement of microbeads and cells with minimal intervention. Programmed transport over one millimeter with cell transport velocities of several micrometers per s is demonstrated. Based on scalable microchip technology, the networks can be integrated with CMOS‐compatible materials and straightforwardly combined with sensing and diagnostic structures. [ABSTRACT FROM AUTHOR]

The energy-efficient manipulation of the properties of functional materials is of great interest from both a scientific and an applied perspective. The application of electric fields is one of the most widely used methods to induce significant changes in the properties of materials, such as their structural, transport, magnetic, and optical properties. This article presents an overview of recent research on the manipulation of the electronic and magnetic properties of various material systems via electrolyte-based ionic gating. Oxides, magnetic thin-film heterostructures, and van der Waals 2D layers are discussed as exemplary systems. The detailed mechanisms through which ionic gating can induce significant changes in material properties, including their crystal and electronic structure and their electrical, optical, and magnetic properties, are summarized. Current and potential future functional devices enabled by such ionic control mechanisms are also briefly summarized, especially with respect to the emerging field of neuromorphic computing. Finally, a brief outlook and some key challenges are presented. [ABSTRACT FROM AUTHOR]

Transverse thermoelectric generation using magnetic materials is essential to develop active thermal engineering technologies, for which the improvements of not only the thermoelectric output but also applicability and versatility are required. In this study, using combinatorial material science and lock-in thermography technique, we have systematically investigated the transverse thermoelectric performance of Sm-Co-based alloy films. The high-throughput material investigation revealed the best Sm-Co-based alloys with the large anomalous Nernst effect (ANE) as well as the anomalous Ettingshausen effect (AEE). In addition to ANE/AEE, we discovered unique and superior material properties in these alloys: the amorphous structure, low thermal conductivity, and large in-plane coercivity and remanent magnetization. These properties make it advantageous over conventional materials to realize heat flux sensing applications based on ANE, as our Sm-Co-based films can generate thermoelectric output without an external magnetic field. Importantly, the amorphous nature enables the fabrication of these films on various substrates including flexible sheets, making the large-scale and low-cost manufacturing easier. Our demonstration will provide a pathway to develop flexible transverse thermoelectric devices for smart thermal management.

Recent research revealed that Sm–Co-based amorphous films prepared by stacking many ultrathin Sm/Co pairs exhibit large in-plane coercivity and realize the zero-field operation of the anomalous Nernst effect (ANE). Here, we investigate the effect of the Sm/Co-pair thickness on the magnetic anisotropy and ANE in Sm–Co-based amorphous films and compare them with a co-sputtered Sm–Co-based amorphous alloy film. We find that the magnetic (magneto-thermoelectric) properties of the co-sputtered film are almost the same as that of the multilayer films with the Sm/Co-pair thickness of ≤1.0 nm (≤3.0 nm). This finding will serve as a guideline for investigating amorphous magneto-thermoelectric materials. [ABSTRACT FROM AUTHOR]

This study examines the spin-wave and magnetic quantum behavior of three-layer graphene-like based on the Heisenberg model. The system is diagonally solved for Hamiltonian quantities using the linear spin wave theory and postponed Green's functions. The effects of exchange coupling, anisotropy, and spin quantum number on the resonance frequency and quantum fluctuation are discussed, providing a basis for regulating resonance frequency and quantum fluctuation.

Important applications of spin polarized low energy electron microscopy (SPLEEM) employ this technique's vector imaging capability to resolve domain wall (DW) spin textures. Studying several thin film systems including Co/W(110), Co/Cu(001) and (Co/Ni)n/W(110), we show that an additional contrast can appear at magnetic DWs. By imaging the magnetization as a function of electron landing energy, electron energies are selected at which the magnetic domain contrast vanishes. Surprisingly, under such conditions of zero contrast between magnetic domains, we observe the appearance of magnetic contrast outlining the DWs. This DW contrast does not depend on the DW spin texture. Instead, our measurements show that this DW contrast results from a combination of the energy-dependence of the spin reflectivity asymmetry of the magnetic film, the finite energy width of the spin polarized electron source, and the dispersion of the magnetic prism array that separates the illumination and imaging columns of the instrument. Awareness of this DW contrast mechanism is useful to aid correct interpretation of SPLEEM images.

The critical‐element‐free ε‐Fe2O3 ferrimagnet exhibits giant magnetic coercivity even at room temperature. It is thus highly attractive material for advanced applications in fields such as spintronics, high‐density data storage, and wireless communication. However, a serious obstacle to overcome is the notoriously challenging synthesis of ε‐Fe2O3 due to its metastable nature. Atomic layer deposition (ALD) is the state‐of‐the‐art thin‐film technology in microelectronics. Herein, it is demonstrated that it has also true potential for the fabrication of amazingly stable in situ crystalline and high‐performance ε‐Fe2O3 thin films from simple (FeCl3 and H2O) chemical precursors at a moderately low deposition temperature (280 °C). Standard X‐ray diffraction and Fourier transfer infrared spectroscopy characterization indicates that the films are of high level of phase purity. Most importantly, precise temperature‐dependent 57Fe Mössbauer spectroscopy measurements verify that the hematite (α‐Fe2O3) trace in the films is below 2.5%, and reveal the characteristic low‐ and high‐temperature transitions at 208–228 K and ≈480 K, respectively, while magnetization measurements confirm the symmetric hysteresis loops expected for essentially phase‐pure ε‐Fe2O3 films. Excitingly, the highly c‐axis oriented film growth, the overall film quality, and the unique magnetic properties remain the same, independently of the substrate material used. [ABSTRACT FROM AUTHOR]

• Large emergent magneto-inductance (EML) is observed in Ni80Fe20 thin films on glass. • EML is enhanced by decreasing the cross-sectional area of Ni80Fe20 thin films. • Frequency response of EML in Ni80Fe20/glass exhibits a Debye-type relaxation property. • EML can be explained by calculation based on the transient domain-wall motion. • EML can be a powerful tool for potential applications in magnetic sensors. We investigate an emergent magneto-inductance (EML) effect using stepwise magnetic field with AC current in Ni 80 Fe 20 and Ni 36 Fe 64 thin films on glass substrates. The properties of the EML effect were evaluated in terms of frequency, stepwise magnetic field, cross-sectional area, and the proportion of Ni and Fe. As a result, a large EML (>1.5 μH) is observed under a low magnetic field of 10 Oe in Ni 80 Fe 20 thin films at room temperature. The EML effect can be enhanced by increasing the stepwise magnetic field increment or decreasing the cross-sectional area of Ni 80 Fe 20 thin films. Ni 80 Fe 20 /glass exhibits a larger EML effect compared to that of Ni 36 Fe 64 /glass, indicating that the EML depends on the strength of induced magnetic anisotropy. The observed EML effect can be explained by theoretical calculation based on the spin motive force owing to the transient current-driven domain-wall motion. These experimental and theoretical findings provide a deeper understanding on the mechanism of EML effect, and pave the way for potential applications, such as miniaturized inductors and magnetic sensors. [ABSTRACT FROM AUTHOR]

In previous experiments, L1 0 FeNi thin films with different surfaces, including (001), (110), and (111), were produced and studied. Each surface defines a different alignment of the crystallographic tetragonal axis with respect to the film's plane, resulting in different magnetic anisotropies. In this study, we use density functional theory calculations to examine three series of L1 0 FeNi films with surfaces (001), (010), and (111), and with thicknesses ranging from 0.5 to 3 nm (from 4 to 16 atomic monolayers). Our results show that films (001) have perpendicular magnetic anisotropy, while (010) favor in-plane magnetization, with a clear preference for the tetragonal axis [001]. We proposed calling this type of in-plane anisotropy fixed in-plane. A film with a surface (111) and a thickness of four atomic monolayers has a magnetization easy axis almost perpendicular to the plane of the film. As the thickness of the (111) film increases, the direction of magnetization rotates towards a tetragonal axis [001], positioned at an angle of about 45° to the plane of the film. Furthermore, the most significant changes in spin and orbital magnetic moments occur at a depth of about three near-surface atomic monolayers. Ultrathin L1 0 FeNi films with varying magnetic anisotropies may find applications in spintronic devices. • The (111) surfaces of L10 FeNi film is more stable than (001) and (010) surfaces. • In films (001) and (010), easy magnetization direction is the tetragonal axis [001]. • For thicker (111) films, easy magnetization direction is [001] (45 deg to the plane). • For ultrathin (111) films it deviates from [001] towards [111] (normal to the plane). • Magnetic anisotropy of thinnest (111) films resembles perpendicular anisotropy. [ABSTRACT FROM AUTHOR]

The application of Co–Pt thin films as functional elements of novel nanoelectronics and spintronics devices requires the formation of a homogeneous ferromagnetic CoPt phase with tunable magnetic properties. A diffusion-controlled synthesis of this ferromagnetic phase can be implemented through the annealing of deposited Co/Pt bilayers. Apart from thermal treatment, both structural and magnetic properties of such layered stacks can be affected by ion preirradiation. In this work, we, therefore, studied the effect of a two-stage process consisting of preirradiation with 110 keV Ar+/N+ ions followed by post-annealing in vacuum at 550°С for 30 min on the evolution of the structural, chemical, and magnetic properties of Co/Pt/substrate and Pt/Co/substrate heterostructures. The results obtained for such two-stage processing were compared to those received after single-stage vacuum annealing. It was found that when ion preirradiation is followed by annealing, the diffusion-driven intermixing of Pt and Co leading to the formation of the ferromagnetic Co–Pt phase is slowed down compared to the non-irradiated samples, which is associated with the barrier effect of implanted projectiles. Furthermore, we demonstrate that preirradiation does not compromise the magnetic properties of the samples. For instance, preirradiation leads to a coercivity increase of up to 38 % compared to the non-irradiated annealed samples which is attributed to the presence of remaining paramagnetic Pt between the grains of the ferromagnetic A1 -CoPt phase. We demonstrate that the applied two-stage processing (consisting of ion preirradiation followed by thermal annealing) of magnetic thin films is a promising approach for tailoring their magnetic properties such as the in-plane coercivity, saturation, and effective magnetization. • CoPt ferromagnetic thin films are promising materials for spintronics applications. • Two-stage (ion & thermal) processing was employed for the formation of the ferromagnetic phase. • Ion preirradiation followed by thermal annealing caused a slowdown of the intermixing in the Co–Pt stack. • Ion preirradiation induced the coercivity increase of up to 38 %. • Two-stage processing is promising for tailoring magnetic properties of Co–Pt films. [ABSTRACT FROM AUTHOR]

Binary magnetic alloys like Coâ€"Pt are relevant for applications as components of magnetic exchange coupled composites. Numerous approaches exist to tune the coercive field of Coâ€"Pt alloys primarily relying on high-temperature processing aiming to realize chemically long-range ordered phases. The peculiarity of Coâ€"Pt is that large coercive field and magnetic anisotropy can be achieved even in chemically disordered alloys relying on short-range order. Here, we study alloying of Coâ€"Pt from bilayers of Pt(14 nm)/Co(13 nm) at temperatures up to 550 °С, where bulk diffusion processes are suppressed and the dominant diffusion mechanism is grain boundary migration. We demonstrate that grain boundary diffusion mechanism can lead to the realization of a homogeneous yet chemically disordered Co56Pt44 alloy at temperatures of 500 °С and higher. A pronounced increase of the coercive field for samples processed at temperatures higher than 400 °С is attributed to short-range ordering. With this work, we pinpoint the grain boundary diffusion as the mechanism responsible not only for the homogenization of binary alloy films but also as a driving force for the realization of short-range order in Coâ€"Pt. Our results motivate further research on grain boundary diffusion as a mechanism to realize chemically long-range ordered phases in Coâ€"Pt alloys. [ABSTRACT FROM AUTHOR]

Magnonics is an emerging field in spintronics, aiming at the development of new-concept magnetic devices processing information via the manipulation of spin waves (SWs) in magnetic nanostructures. One of the most popular SW waveguides exploited currently is ferromagnetic nanostrips. Due to quantization caused by the lateral confinements, the dispersion of SWs propagating in a strip is characterized by a multi-branched structure. Consequently, SWs excited in the system involve superpositions of degenerate modes from different branches of the dispersion curves. In this work, we theoretically study the SW branch hybridization effect for two types of excitation methods, either by using a local oscillating magnetic field or a fast-moving field pulse. The former is based on the resonance effect and the latter on the Cherenkov-like emission mechanism. Micromagnetic simulations yield a variety of SW profiles with rather complex structures, which can be well explained by mode superpositions. These results draw attention to the significance of the SW branch hybridization effect when dealing with SWs in nanostrips and provide new aspects for the manipulation of SWs. [ABSTRACT FROM AUTHOR]

Nanoscale magnetic patterning can lead to the formation of a variety of spin textures, depending on the intrinsic properties of the material and the microstructure. Here we report on the spin textures formed in laterally patterned antiferromagnetic (AF)/ferromagnetic (FM) thin film stripes with a period of 200 nm (100 nm FM/100 nm AF). We make use of the AF to FM phase transition in FeRh thin films at ∼100 °C, thereby creating a nanoscale pattern that is thermally switchable between AF/FM stripes and uniformly FM. A combination of spin-resolved photoemission electron microscopy, magnetic force microscopy, and magnetometry measurements allow direct nanoscale observations of the stray magnetic fields emergent from the nanopattern as well as the underlying magnetisation. Our measurements reveal pinning centres resistant to temperature cycling that govern the modulated spin-texture as well as a sub-texture consisting of grain-driven nanoscale magnetisation structure directed out of the film plane. The nanoscale magnetic structure is thus strongly influenced by the film microstructure. Signatures of exchange bias are not observed, most likely due to the small contact area between the AF and FM regions, combined with the fact that the interfaces between the damaged and undamaged regions are likely to be highly diffuse owing to the lateral scattering of incoming ions. These results show that temperature controllable spin textures can be created in FeRh thin films which could find application in domain wall, microwave, or magnonic devices. [Display omitted] [ABSTRACT FROM AUTHOR]

Nanostructured magnetic materials have gained great interest due to their possible technological applications in electronic and spintronic devices or in medicine as drug carriers. The key issue which decides on their potential industrial utilization is an exhibited type of a magnetization reversal process. Two main approaches used to describe the switching mechanism are the domain wall motion and coherent magnetization rotation, known as the Kondorsky and Stoner–Wohlfarth models, respectively. The reversal modes can be distinguished by angular measurements of hysteresis loops; however, in many experimental reports the dependencies do not precisely follow either of the models. This makes the question of how the magnetization reversal takes place and how to control or modify it one of the unclear and worth investigation issues in the research on magnetic materials. In this paper, we present our studies on the magnetization reversal in the exchange-biased CoO/[Co/Pd] thin films deposited on a flat substrate and on an array of anodized titanium oxide nanostructures. We studied the reversal mechanism using hysteresis loops and First-Order Reversal Curves. Interestingly, instead of the typical for the flat Co/Pd multilayers Kondorsky process, the system shows a crossover between the domain wall motion and the coherent rotation. A similar situation takes place for the pattern sample. Here, we connect this unusual behavior with the interface exchange interaction responsible for the exchange bias effect. [Display omitted] [ABSTRACT FROM AUTHOR]

In this paper, we study the thin-film limit of the micromagnetic energy functional in the presence of bulk Dzyaloshinskii–Moriya interaction (DMI). Our analysis includes both a stationary Γ -convergence result for the micromagnetic energy, as well as the identification of the asymptotic behavior of the associated Landau–Lifshitz–Gilbert equation. In particular, we prove that, in the limiting model, part of the DMI term behaves like the projection of the magnetic moment onto the normal to the film, contributing this way to an increase in the shape anisotropy arising from the magnetostatic self-energy. Finally, we discuss a convergent finite element approach for the approximation of the time-dependent case and use it to numerically compare the original three-dimensional (3D) model with the 2D thin-film limit. [ABSTRACT FROM AUTHOR]

This study considers the equiatomic CoCrNi alloy, a typical multi-principal element alloy (MPEA), which in bulk form, has shown superior mechanical properties and excellent oxidation and corrosion resistance. Such a combination of desirable characteristics motivates further research into the potential use of CoCrNi in thin-film form for various applications. This work aims to grow and optimize the deposition parameters of CoCrNi thin films and investigate their influence on the physical properties. The CoCrNi medium entropy alloy thin films were deposited onto Si/SiO2 substrates by direct current magnetron sputtering at different substrate temperatures and working gas pressures using a pre-alloyed target. The equiatomic polycrystalline composition was obtained at optimized pressure (2 mTorr) and temperature (400 °C). The electrical and magnetic properties were measured and contrasted with the physical properties of the bulk CoCrNi. The obtained magnetic properties indicate stabilization of the ferromagnetic phase in CoCrNi thin films. Anomalous Hall effect has been observed for all studied films. This work shows that deposition conditions (e.g., substrate temperature and working pressure) can be utilized to control the composition and microstructure and tailor the physical properties of the considered MPEA thin films for desired applications. [ABSTRACT FROM AUTHOR]

Herein, the experimental observation of micrometer‐scale magnetic skyrmions at room temperature in several Pt/Co‐based thin film heterostructures designed to possess low exchange stiffness, perpendicular magnetic anisotropy, and a modest interfacial Dzyaloshinskii–Moriya interaction (iDMI) is reported. It is found both experimentally and by micromagnetic and analytic modeling that a low exchange stiffness and modest iDMI eliminates the energetic penalty associated with forming domain walls in thin films. When the domain wall energy density approaches negative values, the remanent morphology transitions from a uniform state to labyrinthine stripes. A low exchange stiffness, indicated by a sub‐400 K Curie temperature, is achieved in Pt/Co, Pt/Co/Ni, and Pt/Co/Ni/Re structures by reducing the Co thickness to the ultrathin limit (<0.3 nm). Similar effects occur in thicker Pt/Co/NixCu1−x structures when the Ni layer is alloyed with Cu. At this transition in domain morphology, skyrmion phases are stabilized by small (<1 mT), perpendicular magnetic fields, and skyrmion motion in response to spin–orbit torque is observed. While the temperature and thickness‐induced morphological phase transitions observed are similar to the well‐studied spin reorientation transition that occurs in the ultrathin limit, the underlying energy balances are substantially modified by the presence of an iDMI. [ABSTRACT FROM AUTHOR]

Materials with significant spin-orbit coupling enable efficient spin-to-charge interconversion, which can be utilized in novel spin electronic devices. A number of elements, mainly heavy metals (HMs), have been identified to produce a sizable spin current (${j}_{s}$), while supplied with a charge current (${j}$), detected mainly in the neighboring ferromagnetic (FM) layer. Apart from the spin Hall angle $\theta _{\text {SH}}\,\,= {j}_{s}/{j}$ , spin Hall conductivity ($\sigma _{\text {SH}}$) is an important parameter, which takes also the resistivity of the material into account. In this work, we present a measurement protocol of the HM/FM bilayers, which enables for a precise $\sigma _{\text {SH}}$ determination. Static transport measurements, including resistivity and magnetization measurements, are accompanied by the angular harmonic Hall voltage analysis in a dedicated low-noise rotating probe station. Dynamic characterization includes effective magnetization and magnetization damping measurement, which enable HM/FM interface absorption calculation. We validate the measurement protocol in Pt and Pt-Ti underlayers in contact with FeCoB and present $\sigma _{\text {SH}}$ of up to ${3.3}\,\times \,{10}^{{5}}$ S/m, which exceeds the values typically measured in other HM, such as W or Ta. [ABSTRACT FROM AUTHOR]

In this review, the technique of resonant soft X-ray reflectivity in the study of magnetic low-dimensional systems is discussed. This technique is particularly appealing in the study of magnetization at buried interfaces and to discriminate single elemental contributions to magnetism, even when this is ascribed to few atoms. The major fields of application are described, including magnetic proximity effects, thin films of transition metals and related oxides, and exchange-bias systems. The fundamental theoretical background leading to dichroism effects in reflectivity is also briefly outlined. [ABSTRACT FROM AUTHOR]

Previously, we reported the aqueous electrodeposition of rare earth - iron group alloys. A key factor was the complexation of the metal ions with various coordination compounds (e.g., aminoacetic acids), without which only the ferrous metal and rare earth hydroxides/oxides are deposited. In this work, samarium cobalt (SmCo) alloys were synthesized using direct current (DC) aqueous electrodeposition. The basic electrolyte solution consisted of 1 M samarium sulfamate, 0.05 M cobalt sulfate, and 0.15 M glycine, resulting in deposits containing >30 at% Sm at 60°C with current density of 500 mA/cm2. Supporting electrolytes (i.e., ammonium salts) decreased the Sm content in the deposit. Crystallinity of deposited films altered from nanocrystalline to amorphous as the Sm content increased. Deposits with high Sm content (32 at%) became isotropic with reduction in magnetic saturation (Ms) and coercivity (Hc). A deposition mechanism involving stepwise reduction of the complexed Sm-Co ions by depositing hydrogen atoms was proposed.

• Antiferromagnetics-based coercivity control in hematite/permalloy heterostructures. • Magnetic and structural studies of epitaxial hematite thin films across the Morin transition. • Thickness dependence of the Interfacial coupling between hematite and permalloy across Morin transition. Interfacial effects between antiferromagnetic (AFM) and ferromagnetic (FM) materials have long been a center of magnetism studies. Aside from the exchange bias occurring at the AFM/FM interface, controlling the coercivity is another significant topic in magnetic recordings. The coercivity of FM materials is often determined through varying grain size, alloy composition, density of defects, etc., which is set during material growth and offers limited room for modification after growth. Hematite (α - F e 2 O 3) is an AFM material that undergoes a temperature-controlled spin-flip transition, the so-called Morin transition. This transition gives an extra degree of freedom making hematite an intriguing component to study the exchange coupling when interfaced with an FM material. In this work, changes in the magnetic properties of soft magnetic permalloy (N i 81 F e 19 , or Py) thin films grown on hematite were studied across the Morin transition. Surprisingly, these samples showed a remarkable change in coercivity during the Morin transition. We attribute this effect to the magnetic domain mixture of hematite during the Morin transition. Our findings present a novel method of controlling the coercivity of plain ferromagnetic thin films. [ABSTRACT FROM AUTHOR]

Magnetic properties of multicomponent alloys depend sensitively on the degree of atomic order on the different crystallographic sites. Here we report the contrast between the magnetic properties of bulk and thin-film samples of the Heusler alloy V 2 FeAl. Arc-melted bulk ingots show no site preference of the elements (A2 structure), whereas magnetron-sputtered thin-film samples display a degree of atomic ordering with a tendency towards XA-type order. Electronic structure calculations favour ferrimagnetic XA-type order, and the effect of different pairwise atomic disorder on the element specific and net magnetic moments are evaluated to reproduce experimental observations. XA-type thin-films with iron moment of 1.24 μ B determined by X-ray magnetic circular dichroism are in agreement with calculation, but the measured net moment of 1.0 μ B per formula unit and average vanadium moment are smaller than expected from calculations. The measured Curie temperature is approximately 500 K. Films with a higher degree of disorder have a lower T C , close to 300 K, with a net moment of only 0.1 μ B at low temperature. The large calculated vanadium moments are destroyed by partial disorder on 4 d vanadium sites. By contrast, the arc-melted and annealed bulk alloy with a fully-disordered A2 structure shows no spontaneous magnetization at any temperature; it is a Pauli paramagnet with dimensionless susceptibility χ v = 2.95 × 10-4. [Display omitted] [ABSTRACT FROM AUTHOR]

This paper reports the magnetic domain imaging and magnetization studies carried out on Fe thin films grown with different thicknesses, namely, 5, 15 nm, 30 nm, 50 nm, 75 nm and 100 nm. Films were grown on Si <100> at two different substrate temperatures, namely, room temperature and 550°C. Based on the detailed studies carried out, it was observed that Fe layer thickness and substrate temperature are important control parameters in tuning the magnetic anisotropy along the in-plane (IP) or out-of-plane (OOP) directions. A crossover from surface to volume anisotropy has been demonstrated with change in film thicknesses. Domain imaging studies carried out on Fe films grown at different substrate temperatures and with different thicknesses aided us to understand the magnetic anisotropy and magnetization reversal mechanisms. [ABSTRACT FROM AUTHOR]

Understanding the role of Landau Lifshitz Gilbert dynamics in describing magnetic domain wall (DW) motion in the creep regime is complicated by the presence of static pinning, but has regained interest due to recently observed directional growth in thin films with significant interfacial Dzyaloshinskii-Moriya interaction. Here, we delve into this directional domain growth behaviour in Pt/Co/Ni-based multi-layers under the influence of combined longitudinal and perpendicular magnetic fields via magneto-optical Kerr effect microscopy. Observations, including the onset field,μ0Honset, where the growth direction reverses by 180 degrees, align with the transient steady-state model predictions. By systematically varying the applied perpendicular magnetic field, we estimate the strength of an effective perpendicular field that acts on the DW during creep movement, which was expectedly found to be much smaller than the applied external field itself. This work further adds to the complexity of asymmetric domain expansion in the creep regime, but also highlights the range of magnetic information that can be extracted from careful analysis of this behavior., (Creative Commons Attribution license.)

Novel Ir1–xCrxO2 thin films have been prepared by reactive co–sputtering deposition. Composition, structure and electric and magnetic behavior have been analyzed by different techniques including EDX, XRR, XRD, SQUID magnetometry, electrical resistivity and XANES and XMCD spectroscopies. Despite the difficulty in growing CrO2 by physical deposition techniques, an Ir1–xCrxO2 solid solution phase could be achieved for 0 ≤ x ≤ 0.8, where the oxidation state of Cr is found to remain as 4+. Both the electrical and the magnetic behavior are shown to starkly depart from those of the parent IrO2 (paramagnetic metal) and CrO2 (half–metal ferromagnet) compounds. In particular, they show a semiconducting behavior, dρ/dT

The static and dynamic magnetization response of the CoFeB/IrMn/CoFeB trilayer system with varying thickness of the antiferromagnetic (AF) IrMn layer is investigated using magnetization hysteresis (M–H) and ferromagnetic resonance (FMR) measurements. The study shows that the two CoFeB layers are coupled via a long-range dynamic exchange effect through the IrMn layer up to a thickness of 6 nm. It is found that with the increase in IrMn layer thickness a nearly linear enhancement of the effective magnetic damping constant occurs, which is associated with the simultaneous influence of spin pumping and interlayer exchange coupling effects. An extrinsic contribution to the linewidth originating from the two-magnon scattering is also discussed. The AF-induced interfacial damping parameter is derived by studying the evolution of damping with inverse CoFeB thickness. The static magnetic measurements also reveal the interlayer exchange coupling across the IrMn layer both at room temperature and low temperature. The asymmetric hysteresis loop and training effect observed at low temperature is related to the presence of a metastable AF domain state. We show that both the static and dynamic magnetic properties of trilayer films can be adjusted over a wide range by changing the thickness of the IrMn spacer layer.

In recent years, the microwave processes in artificial multiferroic media such as electromagnonic crystals have attracted increased research interest due to their potential applications for voltage‐controlled spintronic devices. In contrast to the conventional magnonic crystals, the artificially created periodic structures are characterised by electrically and magnetically tunable band gaps in the wave spectrum where the propagation of the electromagnons is forbidden. In this study, an experimental realisation of an electromagnonic crystal based on a ferrite–ferroelectric–ferrite multilayer has been proposed. The authors have demonstrated for the first time a band‐gap splitting, which arises from an interaction of three fundamental modes of two ferrite films separated by a ferroelectric layer. This splitting manifested itself as an additional stop‐band appearance in the frequency response of the electromagnonic crystal. The obtained band structures are confirmed by numerical modelling using the coupled‐mode approach and the transfer‐matrix method. The authors expect that their results allow exploiting the electromagnonic crystal for enhanced logic control as well as for tunable microwave devices. [ABSTRACT FROM AUTHOR]

The enhancement of coercive field values depending on the measurement angle in a perpendicularly magnetized continuous thin film and the asymmetries in its hysteresis loops are analyzed and discussed by means of Hall effect measurements. Anomalous Hall effect and planar Hall effect contributions to the Hall results are separated to make the asymmetric loops symmetrical. The magnetic properties of the sample are also measured by using a vibrating sample magnetometer and magneto-optic Kerr effect methods. The data obtained by the measurement systems are compared, and the differences in their results are discussed. The results of the work highlight the importance of choosing the correct setup for the measurements and the importance of the measurement angle for the Hall effect studies in magnetic thin films. [ABSTRACT FROM AUTHOR]

A general equation describing the motion of domain walls in a magnetic thin film in the presence of an external magnetic field has been reported in this paper. The equation includes all the contributions from the effects of domain wall inertia, damping and stiffness. The effective mass of the domain wall, the effects of both the interaction of the DW with the imperfections in the material and damping have been calculated. [ABSTRACT FROM AUTHOR]