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A large rotating magnetocaloric effect (RMCE) was always observed in the materials with anisotropic magnetisms, for example, ferromagnetism vs antiferromagnetism or paramagnetism, at different crystallographic directions. In this work, anisotropic ferromagnetic susceptibility is utilized to implement low-field (≤2 T) large RMCE in the textured polycrystalline HoB2 alloy. The x-ray diffraction and scanning electron microstructure results reveal that the arc-melted HoB2 exhibits preferred grain orientation along the solidification direction. The measured rotating magnetic entropy changes (−ΔSR) and refrigeration capacity are 6.27 J/kg K and 73.7 J/kg, respectively, under the magnetic field change of 1 T. They are comparable with those of other materials contributed by anisotropic magnetisms. Our results suggest that the polycrystal HoB2 alloy is a promising material for practical application of magnetic refrigeration based on RMCE. [ABSTRACT FROM AUTHOR]

The magnetically actuated robot has valuable potential in biomedicine, bioengineering, and biophysics for its capability to precisely manipulate particles or biological tissues. However, the deformability of rigid robots with predetermined shapes is limited, which constricts their functions and causes inconvenience for robots' movement in constricted space. In this study, we proposed a feasible and efficient ferrofluid-based robot for the transportation of tiny particles and blocks. In addition, a method to generate a patterned magnetic field is also introduced to model a ferrofluid-based robot with an adaptive shape. Benefiting from the paramagnetism and fluidity of the ferrofluid-based robot, it also demonstrates outstanding motion accuracy and output force on a superhydrophobic surface. Because of its excellent motion characteristics, high motion accuracy, and high measured output force, the proposed ferrofluid-based robot has great advantages in the field of microoperation. The correlation coefficient between the motion trajectory of the ferrofluid-based robot and the motion trajectory of the micro-stages is 0.9967. The position error is less than 1.5% of the total stroke. [ABSTRACT FROM AUTHOR]

We present an experimental and theoretical study of Pauli paramagnetism and martensite stabilization in a near equiatomic NiTi shape memory alloy. We demonstrate a direct correlation between strain-induced shear of the B19′ NiTi lattice and its electronic and thermodynamical features. An increase in the monoclinic angle β from 97.4 to 98° induces a 7% decrease in the magnetic susceptibility because of a shift and deepening of a dip in B19′ density of states at the Fermi level. It also produces a decrease in the B19′ enthalpy, which translates into an increase in the martensite-to-austenite transition temperature by 60 K. [ABSTRACT FROM AUTHOR]

Force detection of magnetic resonance is now able to attain extremely high spin sensitivity. In these setups, microcantilevers were usually used as a sensitive force sensor and, in most cases, have been applied to solid-state samples such as paramagnetic impurities in solids. On the other hand, there are now growing demands for their applications to liquid-state samples in the research areas of life science because many proteins and enzymes are biofunctionally active only in solutions, where they interact with the surrounding water molecules. In this letter, we present an electron paramagnetic resonance (EPR) technique for solution samples using a SiNx nanomembrane and report high-frequency EPR spectroscopy of a microliter-volume frozen solution sample of hemin and myoglobin at multiple frequencies up to 350 GHz. This technique would be particularly useful to obtain more detailed insight into the electronic structure of metalloproteins/metalloenzymes under biologically active conditions. [ABSTRACT FROM AUTHOR]

Graphdiyne (GDY) was prepared by a cross-coupling reaction and its magnetic properties were studied. The results show that the as-prepared GDY is spin-half paramagnetism. GDY shows the increase in the spin density by annealing, and antiferromagnetism appears after annealing at 600°C. The density functional calculations show that (i) the hydroxyl groups on the chain of GDY sheet are the major magnetic sources, and (ii) these hydroxyl groups have the high barrier energy of 1.73 eV for migrating from the ring site to chain site, which can prevent the hydroxyl groups’ clustering and may favor the antiferromagnetism in the annealed GDY. [ABSTRACT FROM AUTHOR]

Experiments for vanadium dioxide show a magnetic transition characterized by a sharp variation in susceptibility associated with the metal-insulator transition at the temperature Tc. The sample is shown to be of Pauli paramagnetism above Tc but of anomalous paramagnetism below Tc. Considering co-contributions of Pauli paramagnetism of residual V4+ ions and Curie-like paramagnetism of V-V dimers, we propose a phenomenological expression for the temperature-dependent susceptibility below Tc, which yields an excellent agreement with the experimental data. The unusual temperature dependence of Curie-like susceptibility below Tc is explained to be due to the fact that every dimer is formed by spin paring at an angle θ close to 180° and hence has an effective spin expressed as Seff = cos (θ/2) which decreases with lowering temperature. The observed metal-insulator and magnetic transitions are argued to be due to a transition from the high-temperature Pauli paramagnetic state of V4+ ions to the low-temperature dimerized state. [ABSTRACT FROM AUTHOR]

Nanoscale chiral skyrmions in noncentrosymmetric helimagnets are promising binary state variables in high-density, low-energy nonvolatile memory. Skyrmions are ubiquitous as an ordered, single-domain lattice phase, which makes it difficult to write information unless they are spatially broken up into smaller units, each representing a bit. Thus, the formation and manipulation of skyrmion lattice domains is a prerequisite for memory applications. Here, using an imaging technique based on resonant magnetic x-ray diffraction, we demonstrate the mapping and manipulation of skyrmion lattice domains in Cu2OSeO3. The material is particularly interesting for applications owing to its insulating nature, allowing for electric field-driven domain manipulation. [ABSTRACT FROM AUTHOR]

We have synthesized transparent, conducting, paramagnetic stannate thin films via rare-earth doping of BaSnO3. Gd3+ (4f7) substitution on the Ba2+ site results in optical transparency in the visible regime, low resistivities, and high electron mobilities, along with a significant magnetic moment. Pulsed laser deposition was used to stabilize epitaxial Ba0.96Gd0.04SnO3 thin films on (001) SrTiO3 substrates, and compared with Ba0.96La0.04SnO3 and undoped BaSnO3 thin films. Gd as well as La doping schemes result in electron mobilities at room temperature that exceed those of conventional complex oxides, with values as high as 60 cm²/V⋅s (n=2.5 x 1020cm-3) and 30 cm²/V⋅s (n=1x1020cm-3) for La and Gd doping, respectively. The resistivity shows little temperature dependence across a broad temperature range, indicating that in both types of films the transport is not dominated by phonon scattering. Gd-doped BaSnO3 films have a strong magnetic moment of ~7 µB/Gd ion. Such an optically transparent conductor with localized magnetic moments may unlock opportunities for multifunctional devices in the design of next-generation displays and photovoltaics. [ABSTRACT FROM AUTHOR]

Monolayer graphene oxide quantum dots (GOQDs) were obtained by oxidative cutting. The magnetic properties of GOQDs were studied. The results show that most of GOQDs are nonmagnetic, and only few of GOQDs are weakly paramagnetic. The ratio of magnetic GOQDs with the average diameter of 4.13, 3.3, and 1.67 nm is 1/14, 1/15, and 1/70, respectively. It is proposed that the edge states magnetism is suppressed by the edge defects and/or the magnetic correlation induced spins cancellation between magnetic fragments of the boundary, and hydroxyl groups on the basal plane are the major magnetic source of magnetic GOQDs. [ABSTRACT FROM AUTHOR]

We report effect of the initial structural order on the resulting magnetic properties of manganese implanted TiO2films. Different microstructures of as-grown TiO2films, namely, amorphous, polycrystalline anatase, and epitaxial anatase, have been implant-doped with Mn+ up to a concentration of 5 at. %. We found that different initial structures lead to different defect and charge carrier concentrations and, as a result, strongly influence the magnetic properties upon implantation. Depending on the initial microstructure, paramagnetism, secondary phases related magnetic properties as well as ferromagnetism could be observed in the films. [ABSTRACT FROM AUTHOR]

Lorentzian-shaped broader three-terminal Hanle (B-3TH) signals are observed in Fe/SiO2/Si tunnel junction devices at 6-300 K. We propose a spin conducting model, which explains all the characteristics of our experimental results, such as field angle dependence and bias dependence of the B-3TH signals, as well as experimental results reported by other groups. It was found that the shape of the B- 3TH signals is determined by the spin depolarization at the Fe/SiO2 interface caused by local magnetic fields, unlike the conventional understanding. The shape of the B-3TH signals, including narrower and inverted Hanle signals, reflects the magnetic order of an ultrathin paramagnetic layer formed at the Fe/SiO2 interface. Our model provides a unified explanation of the B-3TH signals observed in threeterminal Hanle measurements. [ABSTRACT FROM AUTHOR]

The magnetic properties of 2H phase of MoS2 (2H-MoS2) and 1T phase of MoS2 (1T-MoS2) were investigated both experimentally and theoretically. Lithium (Li) intercalation method was used to prepare single-layer MoS2 sheets. It was found that pristine MoS2 (2H-MoS2) exhibited weak diamagnetism. After exfoliating by Li intercalation, the crystal structure transformed from 2H to 1T phase, and the magnetism was significantly enhanced from diamagnetism to paramagnetism accordingly. With further annealing in argon atmosphere, the 2H phase recovered gradually from 1T phase, and the magnetism decreased correspondingly. Using crystal field theory and combining the results of first principle calculation, we conclude that the enhanced magnetism can be attributed to the Mo atoms of 1T-MoS2. [ABSTRACT FROM AUTHOR]

Defect structure of MgB2 bulk and ultrafine particles, synthesized by solid state reaction route, have been investigated mainly by the aid of X-band electron paramagnetic resonance spectrometer. Two different amorphous Boron (B) precursors were used for the synthesis of MgB2, namely, boron 95 (purity 95%-97%, <1.5 µm) and nanoboron (purity >98.5%, <250 nm), which revealed bulk and nanosized MgB2, respectively. Scanning and transmission electron microscopy analysis demonstrate uniform and ultrafine morphology for nanosized MgB2 in comparison with bulk MgB2. Powder X-ray diffraction data show that the concentration of the by-product MgO is significantly reduced when nanoboron is employed as precursor. It is observed that a significant average particle size reduction for MgB2 can be achieved only by using B particles of micron or nano size. The origin and the role of defect centers were also investigated and the results proved that at nanoscale MgB2 material contains Mg vacancies. Such vacancies influence the connectivity and the conductivity properties which are crucial for the superconductivity applications. [ABSTRACT FROM AUTHOR]

Uniform Cu-doped Bi2Te3 hexagonal nanoplates with widths of ∼200 nm and thicknesses of ∼20 nm were synthesized using a solvothermal method. According to the structural characterization and compositional analysis, the Cu2+ ions were found to substitute Bi3+ ions in the lattice. High-level Cu doping induces a lattice distortion and decreases the crystal lattice by 1.17% in the a axis and 2.38% in the c axis. A paramagnetic state is observed in these nanoplates from 2 to 295 K, which is a significant difference from their diamagnetic un-doped Bi2Te3. [ABSTRACT FROM AUTHOR]

A giant magnetocaloric effect has been observed around the Curie temperature, TC∼42 K, in NdMn1.7Cr0.3Si2 with no discernible thermal and magnetic hysteresis losses. Below 400 K, three magnetic phase transitions take place around 380 K, 320K and 42 K. Detailed high resolution synchrotron and neutron powder diffraction (10-400 K) confirmed the magnetic transitions and phases as follows: TN intra∼380K denotes the transition from paramagnetism to intralayer antiferromagnetism (AFl), TN inter∼320K represents the transition from the AFl structure to the canted antiferromagnetic spin structure (AFmc), while TC∼42K denotes the first order magnetic transition from AFmc to canted ferromagnetism (Fmc+F(Nd)) due to ordering of the Mn and Nd sub-lattices. The maximum values of the magnetic entropy change and the adiabatic temperature change, around TC for a field change of 5 T are evaluated to be -ΔSM max∼15.9 J kg-1 K-1 and ΔTad max∼5K, respectively. The first order magnetic transition associated with the low levels of hysteresis losses (thermal <∼0.8 K; magnetic field <∼0.1 T) in NdMn1.7Cr0.3Si2 offers potential as a candidate for magnetic refrigerator applications in the temperature region below 45 K [ABSTRACT FROM AUTHOR]

The magnetic properties of hexagonal Ba(Ti1-xMnx)O3 (x = 1/9, 1/6) samples specifically treated under different thermal conditions are investigated. A magnetic transformation from paramagnetism of as-grown samples to weak ferromagnetism of post-annealed samples is observed at room temperature. Associated with the structural modulation characteristics and dielectric behaviors, our experimental results reveal that the high-temperature ferromagnetism in Mn-doped hexagonal BaTiO3 derives from RIII types of antiphase domain boundaries. Spin glass transitions are observed at Tsg = 48 K and 44 K in the densely doped as-grown and post-annealed samples, respectively, but the transitions are not intrinsic properties of the hexagonal phases. [ABSTRACT FROM AUTHOR]

We have investigated the magnetization reversal induced by carrier doped graphene (Be, B, N, O, or Cl doping) in Ni/Graphene/Co. In undoped case, the magnetic layers have an antiferromagnetic (AFM) coupling and this is still preserved from Be to O doping. We find magnetization reversal from AFM to ferromagnetic interaction induced by Cl doped graphene. In addition, the Ni and the Co layers show the opposite spin asymmetry near the Fermi level and this implies that each layer will generate completely different in-plane spin current in the same direction if an external electric field is applied. [ABSTRACT FROM AUTHOR]

The Z1/2 center in n-type 4H-SiC epilayers-a dominant deep level limiting the carrier lifetime-has been investigated. Using capacitance versus voltage (C-V) measurements and deep level transient spectroscopy (DLTS), we show that the Z1/2 center is responsible for the carrier compensation in n-type 4H-SiC epilayers irradiated by low-energy (250 keV) electrons. The concentration of the Z1/2 defect obtained by C-V and DLTS correlates well with that of the carbon vacancy (VC) determined by electron paramagnetic resonance, suggesting that the Z1/2 deep level originates from VC. [ABSTRACT FROM AUTHOR]

We present a spectromicroscopy study of the two distinct metal-insulator transitions in (V1-xCrx)2O3, x = 0.011. The coexistence of metallic and insulating domains was observed with scanning photoelectron microscopy for both the paramagnetic insulator-paramagnetic metal and paramagnetic metal-antiferromagnetic insulator transitions, evidencing a clear correlation between their nucleation regions. Although these two transitions are very different in nature and underlying mechanism, in both cases the morphology of their phase separation is influenced by structural inhomogeneities. These results demonstrate the general relevance of strain caused by local lattice distortions in guiding the intrinsic tendency towards phase separation in Mott materials. [ABSTRACT FROM AUTHOR]

We present an analytical method for the real-time detection of free radicals from the photodecomposition (ultraviolet radiation, λ = 254 nm) of hydrogen peroxide (H2O2) using frequency-mixing magnetic detection. We monitored the free radicals in situ without catalysts or probe molecules. Both water and H2O2 produced frequency-mixing signals under UV radiation, but the water signal was much weaker. The root mean square amplitude of the frequency-mixing signal was found to depend on the initial H2O2 concentration. Considering the physical properties of the reactants, the frequency-mixing signal is attributed to the generation of paramagnetic free radicals by the photodecomposition of H2O2. [ABSTRACT FROM AUTHOR]

Ferromagnetism at room temperature in (Ti,Co)O2 - δ was controlled by changing its electron density via chemical doping, where the oxygen vacancy δ served as an electron donor. With increasing the electron density, the ferromagnetic anomalous Hall effect and magnetization emerged from a paramagnetic state, while undergoing an insulator to metal transition. This result supports that the electron carriers mediated the ferromagnetic exchange interaction and is consistent with the electric field effect study on the ferromagnetism recently reported [Y. Yamada, K. Ueno, T. Fukumura, H. T. Yuan, H. Shimotani, Y. Iwasa, L. Gu, S. Tsukimoto, Y. Ikuhara, and M. Kawasaki, Science 332, 1065 (2011)]. [ABSTRACT FROM AUTHOR]

Element specific magnetic hysteresis loops of the interlayer exchange coupled CoFeB/Ru/[Co/Ni]4 structure were measured utilizing x-ray magnetic circular dichroism. It was found that the Co/Ni multilayer and the CoFeB layer have Ru thickness dependent oscillatory interlayer coupling. Due to its interlayer coupling with the perpendicularly magnetized Co/Ni multilayer, the CoFeB magnetization direction is slightly tilted out-of-plane from its in-plane magnetic easy axis. Quantitative measurements show that the tilting angle is small (<12°) and that a small in-plane magnetic field (∼50 Oe) applied to this structure will result in a completely in-plane CoFeB magnetization. [ABSTRACT FROM AUTHOR]

We have studied the magnetization of vertically aligned graphene nanoflakes irradiated with nitrogen ions of 100 KeV energy and doses in the range 1011-1017 ions/cm2. The non-irradiated graphene nanoflakes show a paramagnetic contribution, which is increased progressively by ion irradiation at low doses up to 1015/cm2. However, further increase on implantation dose reduces the magnetic moment which coincides with the onset of amorphization as verified by both Raman and x-ray photoelectron spectroscopic data. Overall, our results demonstrate the absence of ferromagnetism on either implanted or unimplanted samples from room temperature down to a temperature of 5 K. [ABSTRACT FROM AUTHOR]

Single-phase PbPd0.81Co0.19O2 film with a body-centered orthorhombic structure was prepared using the sol-gel spin-coating technique and an oxidation treatment. Film resistivity has a power dependence on temperature. The insulator-metal transition temperature was 358 K, markedly higher than the reported values of similar material systems. Ferromagnetism and superparamagnetism coexisted in the film and the ferromagnetism persisted up to 380 K. As temperature increased, the notable increasing tendencies were found for the film's saturation magnetization and for the magnetic field where saturation magnetization decreases abruptly. The special spin gapless band structure and the film's nanograin microstructure are likely responsible for these interesting properties. [ABSTRACT FROM AUTHOR]

A sharp drop in resistance and a magnetization anomaly have been observed in La2/3Ca1/3MnO3 film in zero magnetic field at the BaTiO3 substrate structural phase transition temperature, due to the substrate clamping/strain effect, which is confirmed by Raman scattering. However, the anomalies for both resistance and magnetization were eliminated by a strong external magnetic field. These phenomena indicate that strain can cause colossal resistance and a change in magnetization which resembles the magnetic field effect. The interplay of the external forces (strain and magnetic field) is a good demonstration of the strong coupling between spin and lattice in colossal magnetoresistance materials. [ABSTRACT FROM AUTHOR]

The unusual behavior of negative remanent magnetization (NRM) that is observed in a simple homogeneous system consisting of two uniaxial anisotropies is explained quantitatively using an energy equation derived under the single domain assumption. The relative strength and alignment of the two uniaxial anisotropies and the direction of the applied magnetic field with respect to these anisotropies are identified as the three important factors for NRM. The window showing NRM is wider at larger angles between the two anisotropies and a maximum in NRM occurs near the boundary between NRM and ordinary positive remanent magnetization. [ABSTRACT FROM AUTHOR]

Using density matrix equations of motion and a tight-binding band calculation, we predict all-optical switching between four metastable magnetic states of (III,Mn)As ferromagnets. This switching is initiated non-thermally within 100 fs, during nonlinear coherent photoexcitation. For a single optical pulse, magnetization reversal is completed after ∼100 ps and controlled by the coherent femtosecond photoexcitation. Our predicted switching comes from magnetic nonlinearities triggered by a femtosecond magnetization tilt that is sensitive to un-adiabatic light-induced spin interactions. [ABSTRACT FROM AUTHOR]

We study the proximity effect in Josephson junctions made of electron-doped cuprates Pr2-xCexCuO4 (PCCO). With superconducting electrodes at a fixed doping x = 0.15, we explore the variation of the Josephson coupling with the doping and the thickness of the barrier. We observe Josephson coupling for any type of barrier: antiferromagnetic (AF) metal, AF insulator, or paramagnetic metal. For an x = 0.05 barrier, we can estimate the normal coherence length, ξn = 12 ± 3 nm. Comparing this value with the theoretical prediction, ξn,max = 4.5 nm, we conclude that the proximity effect through a barrier of PCCO x = 0.05 is stronger than expected. [ABSTRACT FROM AUTHOR]

The amphoteric nature of Si/SiO2 interface states in submicron sized metal-oxide-silicon-field-effect-transistors is observed using an enhanced spectroscopic charge pumping method. The method's simplicity and high sensitivity makes it a powerful tool for interrogating the true nature of electrically measured interface states in samples which exhibit extremely low defect densities. The spectroscopic results obtained clearly illustrate a signature 'double peak' density of states consistent with amphoteric Pb center data obtained from electron spin resonance measurements. Since the method is a hybrid of the commonly used charge pumping methodology, it should find widespread use in electronic device characterization. [ABSTRACT FROM AUTHOR]

We study hysteresis in a micron-sized bead: a nonmagnetic matrix embedded with superparamagnetic nanoparticles. These hold tremendous promise in therapeutic applications as heat generating machines. In this letter, we provide a theoretical framework which enables manipulation of heat dissipation by a compatible selection of commercially available beads and the frequency f and amplitude ho of the oscillating field applied in the laboratory. We also introduce a protocol for gradual heating of a local region utilizing return point memory. Easy implementation makes it potentially useful in remedial procedures such as hyperthermia and chemotherapy. [ABSTRACT FROM AUTHOR]

Density functional theory with local spin density approximation is applied to study the evolution of ferromagnetism in SrxPb1-xRuO3 (0≤x≤1). Besides the enhanced Pb-O covalence and Pb-Ru hybridization, the Jahn-Teller effect, which favors the low-spin state (S=0) of Ru4+ in a stretched oxygen octahedra, is found to be the origin of the observed paramagnetism in PbRuO3. With the introduction of Sr, the Pb-Ru hybridization is weakened and an intermediate-spin state (S=1) is preferred via the opposite Jahn-Teller effect in a compressed oxygen octahedra, leading to the appearance of ferromagnetism for x>0.5. Our calculations provide a good explanation of recent experimental findings. [ABSTRACT FROM AUTHOR]

We demonstrate the detection of the Brownian relaxation frequency of 250 nm diameter magnetic beads using a lab-on-chip platform based on current lines for exciting the beads with alternating magnetic fields and highly sensitive magnetic tunnel junction (MTJ) sensors with a superparamagnetic free layer. The first harmonic out-of-phase component of the MTJ response gives the imaginary part of the magnetic bead susceptibility, which peaks at the Brownian relaxation frequency. This work paves the way to on-chip implementation of Brownian magnetorelaxometry in innovative 'lab-on-a-bead' assays for biomolecular recognition. [ABSTRACT FROM AUTHOR]

Magnetic properties and magnetocaloric effect of the Mn5PB2 compound have been investigated. The maximum values of magnetic entropy change -ΔSM at 302 K are 4.93 and 2.64 J kg-1 K-1 for magnetic field changes of 5 and 2 T, respectively, which are closely related with a second-order magnetic transition from the ferromagnetic to the paramagnetic state. The reversible magnetocaloric effect with relatively large magnetic entropy change makes the Mn5PB2 compound (free of rare earths) and Mn5PB2-based materials attractive candidates for room-temperature magnetic refrigeration. [ABSTRACT FROM AUTHOR]

Effect of quenched disorder (QD) caused by oxygen vacancy (OV) and substrate induced inhomogeneous compressive strain, on the magnetic and transport properties of oriented polycrystalline Sm0.55Sr0.45MnO3 thin films is investigated. QD is related intimately to the ordering/disordering of the OVs and controls the paramagnetic-ferromagnetic/insulator-metal transition. OV ordered films show enhanced TC/TIM∼165 K, which is depressed by oxygen annealing. OV disordering realized by quenching reduces TC/TIM. The first order IM transition observed in SSMO single crystals is transformed into nonhysteretic and continuous one in the OV ordered films. QD appears to be diluted by OV disorder/annihilation and results in stronger carrier localization. [ABSTRACT FROM AUTHOR]

Prompted by the generally poor understanding of the nature of magnetic phenomena in 3d-metal doped ZnO, we have undertaken on-line 57Fe Mössbauer spectroscopy on ZnO single crystals in an external magnetic field of 0.6 T, following the implantation of radioactive 57Mn ions at room temperature. The Mössbauer spectra of the dilute Fe impurities are dominated by sextets whose angular dependence rules out an ordered magnetic state (which had been previously proposed) but are well accounted for on the basis of Fe3+ paramagnetic centers on substitutional Zn sites with unusually long relaxation times (>20 ns). [ABSTRACT FROM AUTHOR]

Near room temperature, MnAs films align into two phases, one ferromagnetic and the other paramagnetic. These phases take the intriguing form of nanoscale wires. We have exploited this phase coexistence to form linear arrays of magnetite nanoparticles without the need for photolithography. This is confirmed via extensive scanning probe microscopy. [ABSTRACT FROM AUTHOR]

Substitution of some Cr for Mn atoms in MnCoGe was employed to control the magnetic and structural transitions in this alloy to coincide, leading to a single first-order magnetostructural transition from the ferromagnetic to the paramagnetic state with a giant magnetocaloric effect observed near room temperature. Further increase in the Cr content in the Mn1-xCrxCoGe alloys can induce another first-order magnetoelastic transition from the antiferromagnetic to the ferromagnetic state occurring at lower temperature. The giant magnetocaloric effect as well as the simultaneous tunability of the two magnetic transitions make these materials promising for future cooling applications. [ABSTRACT FROM AUTHOR]

The magnetic state of the low-temperature martensite in a Ni43.5Co6.5Mn39Sn11 magnetic shape memory alloy (MSMA) is disclosed. At temperatures (T) above a critical temperature Tf, the magnetization versus field [M(H)] curves display a sigmoid shape, show no magnetic hysteresis, and can be well fitted according to the Langevin model, confirming that the martensite shows superparamagnetic behavior at T>Tf. On the other hand, the observation of a memory effect during the stop-and-wait protocol and the analysis of dynamic magnetic properties probed by ac susceptibility measurements unequivocally corroborate the superspin glass behavior of interacting magnetic clusters at T

We investigated the in-plane reorientation of magnetization in epitaxial Fe/MnPd bilayers. The samples with various thicknesses of MnPd and Fe layers present a conventional square and an unusual two-step exchange biased hysteresis loops at different temperature. The shape of the loops is reproduced using the coherent rotation model and including the relative orientation of the uniaxial anisotropy with respect to the exchange bias. The parallel and perpendicular uniaxial anisotropies in the ferromagnetic layer are linked to the aligned and the reoriented states, respectively. The magnetic reorientation between the aligned and the reoriented states, which is determined by the competition between the interface exchange coupling and the intrinsic uniaxial energies, is shown to be driven by the temperature, as well as the thickness of MnPd and Fe layers. [ABSTRACT FROM AUTHOR]

This letter reports that both ac susceptibility and electronic transport measurements of the multiferroic compound LuFe2O4 under pressure show that the transition temperature from the paramagnetic state to the ferrimagnetic state decreases with increasing pressure, indicating that the pressure favors the paramagnetic state and suppresses the ferrimagnetic state. Moreover, the minimum of resistivity changes under pressure, which decreases with increasing pressure, appears at the magnetic phase transition temperature. [ABSTRACT FROM AUTHOR]

We demonstrate a simple, low cost, magnetotransport method for rapidly characterizing the magnetic anisotropy and anisotropic magnetoresistance of ferromagnetic devices with uniaxial magnetic anisotropy. This transport technique is the analog of magnetic susceptibility measurements of bulk material but is applicable to very small samples with low total moment. The technique is used to characterize devices fabricated from the dilute magnetic semiconductor (Ga,Mn)As. The technique allows us to probe the behavior of the parameters close to the Curie temperature, in the limit of the applied magnetic field tending to zero. This avoids the complications arising from the presence of paramagnetism. [ABSTRACT FROM AUTHOR]

Comparison between densities of paramagnetic Ge dangling bond defects and shallow acceptor traps at interfaces of the condensation-grown Si1-xGex layers (0.28≤x≤0.93) with thermal SiO2 as a function of Ge fraction, x, reveals quantitative agreement. Moreover, defect densities detected in both magnetic resonance and electrical experiments exhibit reversible passivation-depassivation behavior with respect to hydrogen indicating observation of the same defect (Ge Pb1 center). The corresponding energy level is estimated to lie at 0.35±0.10 eV above the valence band in bulk Si, which makes these defects behave as shallow acceptors in Ge-rich Si1-xGex. [ABSTRACT FROM AUTHOR]

Superparamagnetic fluctuations of magnetization in thin Fe films that coat a sharp W(001) tip are evident in the spin polarization of field emitted electrons. Fluctuations of polarization between four transverse directions that align with the tip <100> directions are consistent with the in-plane biaxial magnetization of Fe films on macroscopic W(001) surfaces. This superparamagnetic behavior imposes a limit to spin polarized vacuum tunneling applications that proves to be more stringent than the suppression of the Curie temperature in thin films due to finite size effects. [ABSTRACT FROM AUTHOR]

Monodisperse superparamagnetic SnO2-coated iron-oxide nanoparticles (∼16.4 nm) have been synthesized via thermal decomposition. The thickness of SnO2 shells can be controlled from 1–5 nm. As-prepared SnO2-coated iron-oxide nanoparticles with high saturation magnetization (18 A m2/kg), are stable up to 600 °C, which can be formed stable ferrofluid. It was suggested that the SnO2 shell acts as a barrier of preventing the growth of γ-Fe2O3 and consequently, avoiding the γ-Fe2O3-to-α-Fe2O3 phase transition at high temperatures. [ABSTRACT FROM AUTHOR]

We report a systematic study of the film thickness dependence (0.1–1 μm) of room-temperature ferromagnetism in pure magnetron-sputtered ZnO thin films wherein a sequential transition from ferromagnetism to paramagnetism and diamagnetism as a function of film thickness is observed. The highest saturation magnetization (MS) value observed is 0.62 emu/g (0.018 μB/unit cell) for a ∼480 nm film. On doping the ZnO film with 1 at. % Mn enhances the MS value by 26%. The ferromagnetic order in ZnO matrix is believed to be defect induced. In addition, on doping with Mn hybridization between the 2p states of O and the 3d states of Mn occurs. [ABSTRACT FROM AUTHOR]

We report pulsed laser deposition synthesis and characterization of polycrystalline Fe1-xCoxSi thin films on Si (111). X-ray diffraction, transmission electron, and atomic force microscopies reveal films to be dense, very smooth, and single phase with a cubic B20 crystal structure. Ferromagnetism with significant magnetic hysteresis is found for all films including nominally pure FeSi films in contrast to the very weak paramagnetism of bulk FeSi. For Fe1-xCoxSi this signifies a change from helimagnetism in bulk, to ferromagnetism in thin films. These ferromagnetic thin films are promising as a magnetic-silicide/silicon system for polarized current production, manipulation, and detection. [ABSTRACT FROM AUTHOR]

We show that effective chemical interactions in an alloy can be tuned by its global magnetic state, which opens exciting possibilities for materials synthesis. Using first-principles theory we demonstrate that at pressure of 20 GPa and at high temperatures, the effective chemical interactions in paramagnetic Fe–Si system are strongly influenced by the magnetic disorder favoring a formation of cubic Fe2Si phase with B2 structure, which is not present in the alloy phase diagram. Our experiments confirm theoretical predictions, and the B2 Fe2Si alloy is synthesized from Fe–Si mixture using multianvil press. [ABSTRACT FROM AUTHOR]

We report on the electrical field control of ferromagnetism (FM) at room temperature in III-N dilute magnetic semiconductor (DMS) films. A GaMnN layer was grown on top of an n-GaN substrate and found to be almost always paramagnetic. However, when grown on a p-type GaN layer, a strong saturation magnetization (Ms) was observed. This FM in GaMnN can be controlled by depletion of the holes in the GaMnN/p-GaN/n-GaN multilayer structures. We have demonstrated the dependence of the FM on the thickness of the p-GaN in this heterostructure and on the applied bias to the GaN p-n junction. The Ms was measured by an alternating gradient magnetometer (AGM) and a strong correlation between the hole concentration near the GaMnN/p-GaN interface and the magnetic properties of the DMS was observed. At room temperature an anomalous Hall effect was measured for zero bias and an ordinary Hall effect for reverse bias in a fully depleted p-GaN layer. This is in close agreement with the AGM measurement results. [ABSTRACT FROM AUTHOR]

Gd nanocapsules, which are stable in air with the protection of graphite shells, are prepared by a modified arc-discharge technique. A size-induced structural transformation from the hexagonal-close-packed (hcp) to the higher-symmetry face-centered-cubic structure is observed. The graphite-coated hcp-Gd nanocapsules display a blocked state below 35 K, superparamagnetism between 35 and 290 K, and typical paramagnetism above 290 K. The hcp-Gd nanocapsules have a magnetic-entropy change -ΔSm of 48.8 J kg-1 K-1 at 6 K for an applied-field change from 1 to 7 T. [ABSTRACT FROM AUTHOR]

We report on the magnetic actuation of superparamagnetic particles in a microfluidic channel. The formation of a highly confined and dynamic plug of particles extending over the cross section of the microchannel is enabled by superposing a static and a time-varying magnetic field. The latter is generated by an electromagnet and focused across the microchannel using microstructured soft magnetic tips. Finite element calculations of the magnetic force distribution do compare well with experiments. Our system allows maximizing the exposure of superparamagnetic particles to a microfluidic flow of interest for integrated lab-on-a-chip applications. [ABSTRACT FROM AUTHOR]