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The current-induced magnetization switching (CIMS) was successfully observed in epitaxial L10-FePt/CrxPt1−x (0 ≤ x ≤ 1) heterostructures grown by molecular beam epitaxy with large perpendicular magnetic anisotropy. With increasing Cr content, the critical switching current density (Jc) in FePt/CrxPt1−x heterostructures exhibited a decreasing trend, where it was greatly reduced by 69% in FePt/Cr (3d) films compared to FePt/Pt (5d) films with strong spin–orbit coupling. Furthermore, the same switching polarities were observed for all FePt/CrxPt1−x samples, indicating that the orbital Hall effect played a dominant role in CIMS for FePt/Cr films because of opposite spin Hall angles for Cr and Pt. Our results will put forward the applications of L10-FePt in collaboration with the orbital Hall effect from 3d metals in current-controlled magnetic random access memory and neuromorphic computing. [ABSTRACT FROM AUTHOR]

A systematic investigation about Tm substitution by rare earth Y atoms in Tm1−xYxGa (0 ≤ x ≤0.8) compounds on the magnetic properties and magnetocaloric effect (MCE) is presented. Among Tm1−xYxGa compounds, Tm0.4Y0.6Ga exhibits the optimized working temperatures around the boiling point of liquid helium and large MCE. It undergoes a ferromagnetic (FM) to antiferromagnetic (AFM) transition at TFA = 2.8 K and an AFM to paramagnetic transition at TN = 5.4 K with increasing temperature, respectively. Moreover, the characteristic of second-order magnetic transition was confirmed on the basis of Arrott plots, rescaled universal curves, mean-field theory criterion, and the quantitative criterion of exponent n. Large MCE with the maximum magnetic entropy change of 6.4, 10.1, and 15.6 J/kg K and the maximum adiabatic temperature change of 2.4, 4.2, and 8.4 K for the field changes of 0–1, 0–2, and 0–5 T was observed, respectively. Consequently, the properties of low working temperatures, the characteristic of second-order magnetic transition, and good performance of MCE indicate that Tm0.4Y0.6Ga compounds could be a promising candidate of magnetocaloric materials in the application of helium liquefaction. [ABSTRACT FROM AUTHOR]

A polycrystalline TmNiAl2 compound with transition temperature near the liquid helium boiling point was successfully synthesized. Magnetic measurements show that FM (ferromagnetic) to FM and FM to PM (paramagnetic) transitions take place at 2.4 K and 4.0 K, respectively. Magnetic entropy change (–ΔSM) is calculated, and its maximal value [(–ΔSM)max] reaches as high as 20.7 J/kg K with the field change of 0–5 T. The low transition temperature together with large (–ΔSM)max at the liquid helium temperature zone originates from the weak spin-spin exchange interaction between Tm atoms. For a clear comparison, the magnetocaloric effect (MCE) of polycrystalline RNiAl2 (R = Tb and Gd) samples was also prepared and investigated. For the TbNiAl2 compound, FIM (ferrimagnetic) to AFM (antiferromagnetic) and AFM to PM transitions occur at 11.0 K and 21.5 K, respectively. As for the GdNiAl2 compound, an FM to PM transition occurs at 30.5 K. The value of (–ΔSM)max under the field change of 0–5 T is calculated to be 11.8 J/kg K and 17.3 J/kg K for TbNiAl2 and GdNiAl2, respectively. Compared with other RNiAl2-series MCE materials, TmNiAl2 exhibits the lowest working temperature and relatively larger (–ΔSM)max. The large MCE at low temperature indicates that TmNiAl2 is competitive among the MCE materials working at a liquid helium temperature zone. [ABSTRACT FROM AUTHOR]

A secondary magnetic transition (spin reorientation transition) below Curie temperature in ErNi was observed via different characterization techniques. Ho-substitution for Er atoms has a great impact on the magnetic property and magnetocaloric effect. The two magnetic transitions change close to each other with 10% of Ho-substitution at the Er site. It is also found that 10% of Ho-substitution contributes up to ∼14.9% of enhancement on the maximal magnetic entropy change (ΔSM) and ∼21.9% of enhancement on the maximal adiabatic temperature change (ΔTad). The maximum value of ΔSM and ΔTad for Ho0.1Er0.9Ni compound is as high as 34 J/kg K and 8.9 K, respectively, under a field change of 0-5 T. The relationship between the maximal ΔSM and the refrigerant temperature width (δTFWHM) for HoxEr1-xNi (0≤×≤1) compounds is analyzed. The enhancement of MCE for Ho0.1Er0.9Ni compound is considered to be resulted from the tendency of merging of spin reorientation transition and ferromagnetic to paramagnetic transition. [ABSTRACT FROM AUTHOR]

We presented a systematic study on the transport properties of the La0.67A0.33MnO3 (LAMO) (A=Ba, Ca) and La0.67Ca0.33MnO3/LaMnO3 (LCMO/LMO) films with the LAMO layer of the thickness from 0 to 50 nm and a fixed LMO thickness of 3 nm. An interface layer with degenerated magnetic and conductive properties has been observed. It is interesting that the dead layer in LBMO is much thinner than that in LCMO. The thickness for the dead layer is, deduced from the conductivity-film thickness relation at 5K, ∼6 nm for LCMO and ∼3 nm for LBMO, essentially weakly dependent of magnetic field. After introducing the LMO buffer layer, the magnetic field dependence is considerably enhanced; a simple estimate indicates that a field of 5 T depresses the layer thickness from ∼6 nm to ∼3 nm. It indicates that the LMO layer enhances the sensitivity of trapped charge carriers at the interface to magnetic field, thus activates the dead layer. [ABSTRACT FROM AUTHOR]

Pt Schottky contacts on (001)-orientated Nb-doped SrTiO3 (NSTO) in both ambient air and vacuum were investigated by the conductive atomic force microscope. The co-existed TiO2 and SrO termination layers were identified on the terrace-structured NSTO surface, where the former possessed a higher forward current than the latter. In ambient air, the barrier height of Pt/NSTO Schottky junction exhibited periodical variation with cyclic terrace plane and step sites, whereas it became homogeneous in ambient vacuum. We suggested that the oxygen absorption and releasing of surface dangling bonds were the origin for reversible changes in transport properties, which indicates a feasible approach for the surface modulation and band structure tailoring of NSTO based heterojunctions. [ABSTRACT FROM AUTHOR]

In-plane magnetic anisotropy has been studied for the (110)-orientated La2/3Ca1/3MnO3 (LCMO) films grown on SrTiO3 (STO) and LaAlO3 (LAO) substrates. Deviation from orthorhombic symmetry is observed in these two series of films, particularly for the films grown above LAO, which suffer from a strong shear strain. A switch of the magnetic easy axis between the [001] and [1-10] axes is observed for the LCMO/LAO films as structure deformation varies, while the LCMO/ STO films exhibit a [001] easy axis. An analytical analysis of the influence of magnetoelastic energy on magnetic anisotropy is performed, and the dominative role of shear strain is revealed. The present work indicates that the lattice distortion provides a feasible approach towards magnetic engineering, leading to abundant magnetic phenomena. [ABSTRACT FROM AUTHOR]

We investigate magnetic properties and magnetocaloric effects of R2CoGa3 (R=Gd, Dy, and Ho) compounds. It is found that all the compounds are ferromagnetic with the Curie temperatures of TC=50, 17, and 10K for R=Gd, Dy, and Ho, respectively. The R2CoGa3 have large magnetic entropy change (ΔS) that arise from the second-order ferromagnetic-to-paramagnetic phase transition. The maximum values of ΔS are found to be –12.6, –10.8, and –13.8 J/kg K with corresponding refrigerant capacity values of 382, 252, and 287 J/kg for a magnetic field change of 0–50 kOe, respectively. The large ΔS values with little or no hysteresis losses as well as wide working temperature spans imply that the R2CoGa3 compounds may serve as promising candidates for magnetic refrigeration. [ABSTRACT FROM AUTHOR]

The magnetic properties and magnetocaloric effects of the ErNi1-xCuxAl (x = 0.2, 0.5, 0.8) compounds have been studied. The sample with x = 0.2 is found to be antiferromagnetic below the Néel temperature of TN = 4.6 K, while the sample x = 0.5 is simply ferromagnetic with a Curie temperature of TC = 5.8 K. In contrast, the sample x = 0.8 exhibits a short-range magnetic order, as revealed by AC magnetic measurements, and the transition temperature is 5.5 K. Large magnetic entropy change (ΔS) without hysteresis losses has been observed around the transition temperature for all the samples. The ΔS displays a peak between 4 K and 10 K, and the maximal values of ΔS are -22.6, -25.9, and -24.8 J/kg K for the field changes of 0-5 T, corresponding to the compositions of x = 0.2, x = 0.5, and x = 0.8, respectively. The large ΔS value as well as no hysteresis loss indicate that ErNi1-xCuxAl can be alternative candidates for magnetic refrigerant working at low temperature (<10 K). [ABSTRACT FROM AUTHOR]

Local surface conduction of the (001)-orientated SrTiO3:Nb crystal with a terrace-structured morphology has been studied by means of conductive atomic force microscope analysis. We found that the surface conductance is inhomogeneous on the atomic scale; it is high near step edges and low on terrace plateaus. The surface conductance fluctuation is susceptible to post annealing, first enhancing and then weakening while repeatedly annealed at 700 °C in vacuum. Considering the fact that the oxygen content is most sensitive to vacuum annealing for the temperatures adopted here, the inhomogeneous conductance implies the difference of oxygen vacancy content at step edges and terrace plateaus. The present work clearly demonstrated the influence of surface microstructure on physical properties, and could be helpful for the understanding of the atomic scale non-uniformity of the ultrathin films fabricated on step-featured SrTiO3 surface. [ABSTRACT FROM AUTHOR]

In this paper, Ag/Bi0.9La0.1FeO3 (BLFO)/La0.7Sr0.3MnO3 sandwich structure was grown epitaxially on SrTiO3 substrates using pulsed laser deposition. Short-circuit photocurrent (Ishort) and frequency dependence of the capacitance were investigated. It reveals that this heterostructure exhibits strong photocurrent responses, the orientation of Ishort depends strongly on the polarization orientations, and it varies monotonically from one orientation to the other as the polarization orientation switching gradually from upward (downward) to downward (upward), the Ishort value becomes zero when the film is in zero polarization states. The intensity of the Ishort can be strengthened by several times after thousands of bipolar electric pulses. Moreover, after polarization fatigue process of bipolar electric pulses or under light illumination, the capacitance of this sandwich structure is always bigger than the original state. However, the magnifying ratio of the capacitance after and before polarization fatigue process or under light illumination decrease with increasing the frequency in the C-f curves. These results suggest that polarization induced surface charge combined with migration of oxygen vacancies is the primary driving force for the varying of interfacial barriers and the oxygen vacancies density near the interface, which in turn leads to different orientations and values of Ishort as well as the differential interfacial capacitance. Our results indicate that the photovoltaic response in ferroelectric BLFO thin films could be further explored for solar light photovoltaic and other capacitor devices applications. [ABSTRACT FROM AUTHOR]