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Recently, we have demonstrated the presence of spin-orbit torque in FeMn/Pt multilayers which, in combination with the anisotropy field, is able to rotate its magnetization consecutively from 0° to 360° without any external field. Here, we report on an investigation of the static and dynamic magnetic properties of FeMn/Pt multilayers using the combined techniques of magnetometry, ferromagnetic resonance, inverse spin Hall effect, and spin Hall magnetoresistance measurements. The FeMn/Pt multilayer was found to exhibit ferromagnetic properties, and its temperature dependence of saturation magnetization can be fitted well using a phenomenological model by including a finite distribution in Curie temperature due to subtle thickness variations across the multilayer samples. The non-uniformity in static magnetic properties is also manifested in the ferromagnetic resonance spectra, which typically exhibit a broad resonance peak. A damping parameter of around 0.106 is derived from the frequency dependence of ferromagnetic resonance linewidth, which is comparable to the reported values for other types of Pt-based multilayers. Clear inverse spin Hall signals and spin Hall magnetoresistance have been observed in all samples below the Curie temperature, which corroborate the strong spin-orbit torque effect observed previously. [ABSTRACT FROM AUTHOR]

La1-xSrxMnO3 nanocrystals were grown using a microemulsion approach with different water-to- surfactant ratios Rw resulting in diameters between 20 and 40 nm. The variation of Rw entails a variation in the Sr concentrations between x=0.35 and 0.50. This technique allows the controlled growth of structurally well-defined nanoparticles using the same calcination conditions. With decreasing particle size, the unit-cell volume increases together with the Mn–O bond length, while the Mn–O–Mn bond angle was found to decrease. The size-dependent change of structural properties is possibly related to surface effects or disorder. With the decrease in particle size, the ferromagnetic ordering temperature TC decreases significantly by up to 20%. The reduction of TC can be well understood with respect to the structural changes: the increase of Mn–O bond length and the decrease of Mn–O–Mn bond angle weaken the double-exchange coupling and hence reduce TC. In addition the intrinsic finite-size effect reduces TC. The observed size-induced change of magnetic properties may allow for a controlled manipulation of magnetism in La1-xSrxMnO3 nanoparticles by varying the particle size. [ABSTRACT FROM AUTHOR]

FeMn-based spin valves with a gadolinium layer have been fabricated by magnetron sputtering. The magnetoresistive properties of the spin valves have been investigated at temperatures of 80-293K. Temperature-induced switching between low- and high-resistance magnetic states has been revealed. Realization of the low- or high-resistance states depends on which magnetic moment dominates in the exchange-coupled Gd/CoFe, of Gd or CoFe. It has been shown that the switching temperature depends on the thickness of the gadolinium layer. [ABSTRACT FROM AUTHOR]

The perpendicular exchange bias in NiO(antiferromagnet)/Co(ferromagnet) polycrystalline layer films is studied. It is found that the NiO layer forces the Co layer magnetization to be oriented perpendicular to the film plane in a greater thickness range than is found in the Au/Co/Au system. Simultaneously, a large coercivity and a significant perpendicular exchange bias field were observed that are owing to the interlayer exchange bias coupling between NiO and Co, which supports the perpendicular magnetic anisotropy of the Co layer. These findings are confirmed by magnetometry and magnetoresistance measurements. [ABSTRACT FROM AUTHOR]

The magnetic, thermodynamic, and electrical/thermal transport properties of the caged-structure quasi-skutterudite Gd3Ir4Sn13 are re-investigated. The magnetization M(T), the specific heatCp(T)Cp(T), and the resistivityρ(T)ρ(T) reveal a double-phase transition—at TN1?~?10?K and at TN2?~?8.8?K—which was not observed in the previous report on this compound. The antiferromagnetictransition is also visible in the thermal transport data, thereby suggesting a close connection between the electronic and lattice degrees of freedom in this Sn-based quasi-skutterudite. The temperature dependence of ρ(T)ρ(T) is analyzed in terms of a power-law for resistivity pertinent to Fermi liquid picture. Giant, positive magnetoresistance (MR)?≈?80% is observed in Gd3Ir4Sn13 at 2?K with the application of 9?T. The giant MR and the double magnetic transition can be attributed to the quasi-cages and layered antiferromagneticstructure of Gd3Ir4Sn13 vulnerable to structural distortions and/or dipolar or spin-reorientation effects. The giant value of MR observed in this class of 3:4:13 type alloys, especially in a Gd-compound, is the highlight of this work. [ABSTRACT FROM AUTHOR]

The magnetic, thermodynamic, and electrical/thermal transport properties of the caged-structure quasi-skutterudite Gd3Ir4Sn13 are re-investigated. The magnetization M(T), the specific heatCp(T)Cp(T), and the resistivityρ(T)ρ(T) reveal a double-phase transition—at TN1?~?10?K and at TN2?~?8.8?K—which was not observed in the previous report on this compound. The antiferromagnetictransition is also visible in the thermal transport data, thereby suggesting a close connection between the electronic and lattice degrees of freedom in this Sn-based quasi-skutterudite. The temperature dependence of ρ(T)ρ(T) is analyzed in terms of a power-law for resistivity pertinent to Fermi liquid picture. Giant, positive magnetoresistance (MR)?≈?80% is observed in Gd3Ir4Sn13 at 2?K with the application of 9?T. The giant MR and the double magnetic transition can be attributed to the quasi-cages and layered antiferromagneticstructure of Gd3Ir4Sn13 vulnerable to structural distortions and/or dipolar or spin-reorientation effects. The giant value of MR observed in this class of 3:4:13 type alloys, especially in a Gd-compound, is the highlight of this work. [ABSTRACT FROM AUTHOR]

Magnetoresistance effects observed in ferromagnet/superconductor (FM/SC) hybrids, FM/SC bilayers (BLs) and FM/SC/FM trilayers (TLs), have attracted much interest. Here, we focus on the stray-fields-based superconducting magnetoresistance effect (sMRE) observed in Co(d Co)/Nb(dNb)/Co(dCo) TLs with sufficiently thick Co outer layers so that out-of-plane magnetic domains (MDs) and MDs walls (MDWs) emerge all over their surface when subjected to a parallel external magnetic field, Hex, equal to the coercive field, Hc. To explore the conditions necessary for maximization of the sMRE, we focus on the different kinds of the stray dipolar fields, Hdip, that emerge at the interior of the out-of-plane MDs and at the boundaries of MDWs; these have a different inherent tendency to create straight and semi-loop vortices, respectively. In the recent literature, the creation of straight and semi-loop vortices has been addressed at some extent both theoretically [Laiho et al., Phys. Rev. B 67, 144522 (2003)] and experimentally [Bobba et al., Phys. Rev. B 89, 214502 (2014)] for the case of FM/SC BLs. Here, we address these issues in FM/SC/FM TLs in connection to the sMRE. Specifically, we focus on an experimental finding reported recently [D. Stamopoulos and E. Aristomenopoulou, J. Appl. Phys. 116, 233908 (2014)]; strong magnetostatic coupling of the FM outer layers is accompanied by an intense sMRE in TLs in which the thickness of the SC interlayer, dSC, matches the width of MDWs, DMDWs. To investigate this finding, we employ simulations-modeling and energy-considerations and propose two quantitative criteria that facilitate the creation of straight vortices over semi-loop ones. The first focuses on the maximization of the stray Hdip that occur at the interior of the out-of-plane MDs. The second enables the estimation of a crossover between the preferable creation of one kind of vortices over the other. Both criteria respond well, when tested against experimental results. These generic criteria on the interference between dSC and DMDWs can assist the design of cryogenic devices based on FM/SC/FM TLs. [ABSTRACT FROM AUTHOR]

We investigate the effect of a single magnetic bead (MB) on the domain wall (DW) pinning/depinning fields of a DW trapped at the corner of an L-shaped magnetic nanodevice. DW propagation across the device is investigated using magnetoresistance measurements. DW pinning/depinning fields are characterized in as-prepared devices and after placement of a 1 μm-sized MB (Dynabeads® MyOne™) at the corner. The effect of the MB on the DW dynamics is seen as an increase in the depinning field for specific orientations of the device with respect to the external magnetic field. The shift of the depinning field, ΔBdep = 4.5-27.0 mT, is highly stable and reproducible, being significantly above the stochastic deviation which is about 0.5 mT. The shift in the deppinning field is inversely proportional to the device width and larger for small negative angles between the device and the external magnetic field. Thus, we demonstrate that DW-based devices can be successfully used for detection of single micron size MB. [ABSTRACT FROM AUTHOR]

Magnetic materials are investigated in order to enable a new type of Thermally Assisted Magnetic Random Access Memory (TAS-MRAM). A TAS-MRAM materials stack that is robust against the 400 °C process temperatures required for embedded integration with complementary metal oxide silicon processes is demonstrated. In unpatterned sheet film stacks, a stable resistance-area product, tunneling magnetoresistance (MR)>100%, and temperature-dependent exchange bias of 1500 Oe after 400 °C anneal are shown for this stack. It is further shown that by doping the sense and storage layers with Ta using thin laminations of Ta/CoFeB, the moment of each layer can be reduced by more than 40% without a major reduction in MR. In patterned nanopillar devices, it is shown that by reducing the moment of the sense and storage layers with laminations of Ta, and by adding a second MgO barrier, the resistance versus applied field loop quality is maintained, while the read field is reduced by more than 40% and devices survive 108 write cycles without breakdown or significant degradation. [ABSTRACT FROM AUTHOR]

We investigated the nature of transport and magnetic properties in SrIr0.5Ru0.5O3 (SIRO), which has characteristics intermediate between a correlated non-Fermi liquid state and an itinerant Fermi liquid state, by growing perovskite thin films on various substrates (e.g., SrTiO3 (001), (LaAlO3)0.3(Sr2TaAlO6)0.7 (001), and LaAlO3 (001)). We observed systematic variation of underlying substrate dependent metal-to-insulator transition temperatures (TMIT ~ 80K on SrTiO3, ~90K on (LaAlO3)0.3(Sr2TaAlO6)0.7, and ~ 100K on LaAlO3) in resistivity. At temperature 300K⩾T⩾TMIT, SIRO is metallic and its resistivity follows a T3/2 power law, whereas insulating nature at T25 K, with negative MR ∼ B1/2 and positive MR ∼ B2; consistent with the localized-to-normal transport crossover dynamics. Furthermore, observed spin glass like behavior of SIRO on SrTiO3 (001) at T<25K in the localized regime validates the hypothesis that (Anderson) localization favors glassy ordering. These remarkable features provide a promising approach for future applications and of fundamental interest in oxide thin films. [ABSTRACT FROM AUTHOR]

The emergence of ferromagnetism in materials where the bulk phase does not show any magnetic order demonstrates that atomically precise films can stabilize distinct ground states and expands the phase space for the discovery of materials. Here, the emergence of long-range magnetic order is reported in ultrathin (111) LaNiO3 (LNO) films, where bulk LNO is paramagnetic, and the origins of this phase are explained. Transport and structural studies of LNO(111) films indicate that NiO6 octahedral distortions stabilize a magnetic insulating phase at the film/substrate interface and result in a thickness-dependent metal–insulator transition at t = 8 unit cells. Away from this interface, distortions relax and bulk-like conduction is regained. Synchrotron x-ray diffraction and dynamical x-ray diffraction simulations confirm a corresponding out-of-plane unit-cell expansion at the interface of all films. X-ray absorption spectroscopy reveals that distortion stabilizes an increased concentration of Ni2+ ions. Evidence of long-range magnetic order is found in anomalous Hall effect and magnetoresistance measurements, likely due to ferromagnetic superexchange interactions among Ni2+–Ni3+ ions. Together, these results indicate that long-range magnetic ordering and metallicity in LNO(111) films emerges from a balance among the spin, charge, lattice, and orbital degrees of freedom. [ABSTRACT FROM AUTHOR]

The La0.8Na0.1MnO3 oxide was prepared by the solid-state reaction and annealed in air. The X-ray diffraction data reveal that the sample is crystallized in a rhombohedral structure with R3c space group. Magnetic study shows a second-order magnetic phase transition from ferromagnetic to paramagnetic state at the Curie temperature TC = 295 K. In addition, the magnetizations as a function of temperature and the magnetic field is used to evaluate the magnetic entropy change ΔSM. Then, we have deduced that the La0.8Na0.1MnO3 oxide has a large magnetocaloric effect at room temperature. Such effect is given by the maximum of the magnetic entropy change ΔSMmax=5.56, and by the Relative cooling power (RCP) factor which is equal to 235 under a magnetic field of 5 T. Moreover, the magnetic field dependence of the magnetic entropy change is used to determine the critical exponents β, γ, and δ which are found to be β=0.495, γ=1.083, and δ=3.18. These values are consistent with the prediction of the mean field theory (β=0.5, γ=1, and δ=3). Above all, the temperature dependence of electrical resistivity shows a metal-insulator transition at Tρ. The electrical resistivity decrease when we apply a magnetic field giving a magnetoresistance effect in the order of 60% at room temperature. [ABSTRACT FROM AUTHOR]

The La0.8Na0.1MnO3 oxide was prepared by the solid-state reaction and annealed in air. The X-ray diffraction data reveal that the sample is crystallized in a rhombohedral structure with R3c space group. Magnetic study shows a second-order magnetic phase transition from ferromagnetic to paramagnetic state at the Curie temperature TC = 295 K. In addition, the magnetizations as a function of temperature and the magnetic field is used to evaluate the magnetic entropy change ΔSM. Then, we have deduced that the La0.8Na0.1MnO3 oxide has a large magnetocaloric effect at room temperature. Such effect is given by the maximum of the magnetic entropy change ΔSMmax=5.56, and by the Relative cooling power (RCP) factor which is equal to 235 under a magnetic field of 5 T. Moreover, the magnetic field dependence of the magnetic entropy change is used to determine the critical exponents β, γ, and δ which are found to be β=0.495, γ=1.083, and δ=3.18. These values are consistent with the prediction of the mean field theory (β=0.5, γ=1, and δ=3). Above all, the temperature dependence of electrical resistivity shows a metal-insulator transition at Tρ. The electrical resistivity decrease when we apply a magnetic field giving a magnetoresistance effect in the order of 60% at room temperature. [ABSTRACT FROM AUTHOR]

Electronic transport across a FeMg8 magnetic superatom and its dimer has been investigated using a density functional theory combined with Keldysh nonequilibrium Green's-function formalism. For a single cluster, our studies for the cluster supported in various orientations on a Au(100) surface show that the transport is sensitive to the contact geometry. Investigations covering the cases where the axes of Mg square antiprism are 45°, perpendicular, and parallel to the transport direction, show that the equilibrium conductance, transferred charge, and current polarizations can all change significantly with orientation. Our studies on the transport across a magnetic superatom dimer FeMg8-FeMg8 focus on the effect of electrode contact distance and the support. The calculated I-V curves show negative differential resistance behavior at larger electrode-cluster contact distances. Further, the equilibrium conductance in ferromagnetic state shows an unusually high spin polarization that is about 81.48% for specific contact distance, and a large magnetoresistance ratio exceeding 500% is also found. The results show that the superatom assemblies can provide unusual transport characteristics, and that the spin polarization and magnetoresistance can be controlled via the contact geometry. [ABSTRACT FROM AUTHOR]

This study presents the effects of substitution of Zn2+ for Co2+ at low concentrations and the effects of temperature variations on the structural, magnetic, and magnetostrictive properties of cobalt ferrite. Although the Zn-substituted cobalt ferrite samples, Co1-xZnxFe2O4 (x = 0.02, 0.04, 0.06, 0.09, and 0.17) did not show observable changes in crystal structure, the magnetic and magnetostrictive properties were strongly affected. The variation in magnetic susceptibility with composition can be related to the variations in magnetization, coercive field and magnetocrystalline anisotropy. The changes in coercive field were found to be primarily due to the variations in the magnetocrystalline anisotropy. The effect of magnetocrystalline anisotropy on magnetization was stronger at lower cation concentration than at higher concentrations. The decrease in magnetization around 150 K is attributed to the high magnetocrystalline anisotropy at low temperatures which prevented the maximum applied field of 4 MA/m from causing the saturation of magnetization in the samples. Because the magnetocrystalline anisotropy was determined with the magnetization data using the Law of Approach to saturation magnetization, the reliability of the result was found to decrease with decrease in temperature. Peak-to-peak magnetostriction amplitude and the strain sensitivity decreased with increase in Zn substitution. [ABSTRACT FROM AUTHOR]

Highlights • Spintronic devices based on domain wall (DW) devices have attracted great interest. • Domain wall racetrack memory has the potential for high-density storage. • Precise control of domain wall motion is a challenge. • We have studied the use of nanoscale compositional variation to pin the domain walls. • To achieve nanoscale compositional mixing, Cr crossbars were used. • Moreoever, we have carried out a novel minor loop investigation of magnetoresistance. • Minor loop study has provided a better understanding of the underlying physics. Abstract Magnetic domain wall memory technology, wherein the information is stored in magnetic domains of multiple magnetic nanowires, is a potential concept proposed to store the large amount of digital data in the near future, which is generated due to the widespread use of social media and computing devices. However, one of the technological challenges which remains to be solved in domain wall memory is the controllable pinning of the domain walls at the nanometer scale. Here, we demonstrate the possibility to stabilize domain walls with nanoscale modification of magnetic properties by using thermal diffusion of elements from crossbar configuration. We have inspected and evaluated the magnetic properties of the nanowires using Kerr microscopy. The pinning field induced by Cr diffusion of our Ni 80 Fe 20 nanowire was estimated to be about 8 kA/m as determined from minor loop (magnetoresistance vs. magnetic field) measurements. The proposed concept can potentially be used in future domain wall memory applications. [ABSTRACT FROM AUTHOR]

Abstract We report measurements of the magnetoresistance (MR) of platinum in Pt/NiO bilayers made with well textured NiO polycrystalline films over a wide temperature range. We show that the MR arises from two sources, the spin Hall magnetoresistance (SMR) and the anisotropic magnetoresistance (AMR). The latter results from the magnetic proximity effect of Pt in atomic contact with one of the antiferromagnetic NiO sublattices. The SMR is produced by the charge current generated in the Pt layer by the spin current back reflected from the antiferromagnetic insulating (AFI) NiO film through the inverse spin Hall effect (ISHE). As previously observed in Pt with NiO in the form of bulk crystals or epitaxial films, here the SMR exhibits oscillations in the field angle variation shifted by 90° relative to that observed in the insulating ferrimagnet yttrium iron garnet (YIG). Measurements in the temperature range 10–300 K show that the SMR increases with temperature while the AMR remains constant. The total magnetoresistance of Pt/NiO measured at room temperature with well textured NiO polycrystalline films is substantially larger than the values reported for crystalline or epitaxial NiO. [ABSTRACT FROM AUTHOR]

Abstract Polycrystalline NiCrGa half Heusler alloy, which is predicted to be a half-metallic ferromagnet from first principles calculations, has been synthesized by arc meting technique and its structural, magnetic as well as the electronic properties have been studied. The measured x-ray diffraction (XRD) pattern shows the signature of a disordered structure. Magnetization and magnetoresistance measurements indicate a competition between ferromagnetic and antiferromagnetic correlations in the sample, with no evidence of long range magnetic order down to the lowest temperature (2 K) and highest magnetic field (70 kOe) studied. The experimentally observed structural and magnetic properties are found to be significantly different from the theoretically predicted properties of the ordered cubic C1 b structure. To probe into the possibility of the presence of atomic disorder in the system, we have performed theoretical calculations using the spin-polarized-relativistic Korringa-Kohn-Rostoker method (SPR-KKR). By comparing the experimental data from XRD, magnetization, photoelectron spectroscopy measurements and theoretical calculations, we conclude that NiCrGa has significant amount of atomic disorder. Although, the ordered structure is energetically more stable than the disordered structures, we find that after synthesis, the system tends to stabilize in a disordered structure. The nature of the disorder has been ascertained from experiments and the corresponding electronic structure and magnetic properties have been obtained. With this atomic disorder present in the sample, the ferromagnetic ordering is disturbed and the spin polarization is consequently reduced. [ABSTRACT FROM AUTHOR]

Abstract We present a study of the magnetic phase diagram and the magnetoresistance of a Gd–Tb–Dy–Ho–Lu "ideal" hexagonal high-entropy alloy (HEA), composed of the elements from the heavy half of the rare earth series only. The phase diagram contains an antiferromagnetic (AFM) state, a field-induced ferromagnetic (FM) state above the AFM-to-FM spin-flop transition and a low-temperature spin-glass state. The complex (H , T) phase diagram is a result of competition between the periodic potential arising from the electronic band structure that favors periodic magnetic ordering, the substitutional-disorder-induced random local potential that favors spin-glass-type spin freezing in random directions, the Zeeman interaction with the external magnetic field that favors spin alignment along the field direction and the thermal agitation that opposes any spin ordering. The magnetoresistance reflects complexity of the (H , T) phase diagram. Its temperature dependence can be explained by a continuous weakening and final disappearance of the periodic potential upon cooling that leads to the destruction of long-range ordered periodic magnetic structures. The magnetoresistance is large only at temperatures, where the AFM and field-induced FM structures are present and exhibits a maximum at the critical field of the AFM-to-FM transition. Within the AFM phase, the magnetoresistance is positive with a quadratic field dependence, whereas it is negative with a logarithmic-like field dependence within the field-induced FM phase. At lower temperatures, the long-range periodic spin order "melts" and the magnetoresistance diminishes until it totally vanishes within the low-temperature spin glass phase. The magnetoresistance is asymmetric with respect to the field sweep direction, reflecting nonergodicity and frustration of the spin system. Highlights • Hexagonal Gd–Tb–Dy–Ho–Lu is a prototype of an ideal high-entropy alloy. • Its magnetic phase diagram contains antiferromagnetic, ferromagnetic and spin glass phases. • Magnetoresistance (MR) reflects complexity of the magnetic phase diagram. • MR is large only at temperatures where long-range magnetic structures are present. • MR exhibits a maximum at the field-induced antiferromagnetic-to-ferromagnetic transition. [ABSTRACT FROM AUTHOR]

Abstract For Ni-Mn-Z based (Z = Sn, In, Sb) alloys, the martensite transformation (MT) and magnetic transition in austenite state create opposite magnetic cooling effect, which offsets each other when the first-order MT (FOMT) coincides with the second-order magnetic transition (SOMT). In the present study, two successive magnetization peaks are introduced in a Ni 48.4 Fe 1.1 Mn 38.5 Sn 12.0 alloy by creation of a partial overlap between reverse MT and magnetic transition in the austenite phase with 1.1 at.% Fe-doping. In addition, significant enhancement of the magnetization difference (ΔM) between martensite/austenite phases is achieved. Consequently, an inverse magnetocaloric effect (IMCE) associated with a positive isothermal magnetic entropy change (ΔS M) of 9.6 J/kg∙K and a working temperature interval (ΔT FWHM) of 306–314 K is found under an external magnetic field of 5.0 T in the reverse MT and T C A temperature range. This IMCE is followed by a conventional magnetocaloric effect (CMCE) with a negative ΔS M of −2.7 J/kg∙K and ΔT FWHM of 316–339 K under 5.0 T. By taking advantage of these two successive MCEs using a special designed device, large caloric cooling effect with enhanced working temperature interval may be of interesting for practical room-temperature refrigeration applications. Graphical abstract Image 1 Highlights • Doping of 1.1 at.% Fe in Ni 50 Mn 38 Sn 12 alloy enhanced the magnetization of austenite and decreased that of martensite. • The reverse martensite transformation in Ni 48.4 Fe 1.1 Mn 38.5 Sn 12.0 alloy is interrupted by the austenite magnetic transition. • An inverse MCE with ΔS M = 9.6 J/kg∙K, followed by a direct MCE with ΔS M = −2.7 J/kg∙K under 5.0 T is found in Fe 1.1 alloy. [ABSTRACT FROM AUTHOR]

Spin-polarized scanning tunneling microscopy (SP-STM) measures magnetoresistance with atomic resolution. While various methods for achieving SP probes have been developed, each is limited with respect to fabrication, performance, and operating conditions. In this study, we present the fabrication and use of SP-STM tips made from commercially available antiferromagnetic Mn88Ni12 foils. The tips are intrinsically SP, which is attractive for exploring magnetic phenomena in the zero field limit. The tip material is relatively ductile, is straightforward to etch, and has a Néel temperature exceeding 300 K. We benchmark the topographic and spectroscopic performance of our tips and demonstrate their spin sensitivity by measuring the two-state switching of holmium single atom magnets on MgO/Ag(100). [ABSTRACT FROM AUTHOR]

In this study, we investigate the spin transport in normal metal (NM)/insulator (I)/topological insulator (TI) coupled to ferromagnetic insulator (FI) structures. In particular, we focus on the barrier thickness dependence of the spin transport inside the bulk gap of the TI with FI. The TI with FI is described by two-dimensional (2D) Dirac Hamiltonian. The energy profile of the insulator is assumed to be a square with barrier height V and thickness d along the transport-direction. This structure behaves as a tunnel device for 2D Dirac electrons. The calculation is performed for the spin conductance with changing the barrier thickness and the components of magnetization of FI layer. It is found that the spin conductance decreases with increasing the barrier thickness. Also, the spin conductance is strongly dependent on the polar angle h, which is defined as the angle between the axis normal to the FI and the magnetization of FI layer. These results indicate that the structures are promising candidates for novel tunneling magnetoresistance devices. [ABSTRACT FROM AUTHOR]

The phenomenon of spin resonance of two-dimensional electrons confined in a 16 nm AlAs quantum well is studied in the quantum Hall effect regime near filling factor 1. At a temperature of T = 0.5K, spin resonance is not observed directly at filling factor ν = 1, but it is found already with slight deviation from it and at the increase in the temperature of the sample. The dependence of the resonance amplitude on the filling factor has two maxima near filling factors ν ≈ 0.9,1.1 symmetric with respect to ν = 1. The temperature dependences of the spin resonance amplitude near different filling factors are studied. It occurs that the resonance amplitude decreases with decreasing temperature T directly at filling factor 1. With deviation from it, the character of the temperature dependence changes. At ν ≈ 0.9,1.1, the electron paramagnetic resonance amplitude increases with decreasing T. Near filling factor 1, the temperature dependence of the amplitude is with good accuracy proportional to the temperature derivative of the longitudinal magnetoresistance measured at the same. However, quantitative agreement is violated when ν ≠ 1.These experimental observations indicate that the detection of spin resonance at filling factor 1 is based on the sensitivity of the longitudinal magnetoresistance to heating caused by the resonant absorption of microwave radiation, but this mechanism no longer works when ν ≠ 1. [ABSTRACT FROM AUTHOR]

In this work, we performed magnetoresistance measurement in a hybrid system consisting of an arc-shaped quantum point contact (QPC) and a flat, rectangular QPC, both of which together form an electronic cavity between them. The results highlight a transition between collimation-induced resistance dip to a magnetoresistance peak as the strength of coupling between the QPC and the electronic cavity was increased. The initial results show the promise of hybrid quantum system for future quantum technologies. [ABSTRACT FROM AUTHOR]

We report electrical transport and anisotropic magnetic properties of Mn-intercalated 2H-TaS2, a layered transition-metal dichalcogenide with a hexagonal structure. The single crystal MnxTaS2 with x = 1/3 exhibits a transition from paramagnetism to ferromagnetism near 70 K, below which both the magnetoresistance and magnetization properties present strong anisotropic behavior. Its anisotropic magnetoresistance effect and in-plane soft ferromagnetic property suggests that this layered material would be a good candidate for exploring the physics of two-dimensional ferromagnetism. [ABSTRACT FROM AUTHOR]

Inserting an antiferromagnetic layer of NiO between Pt and Y3Fe5O12 (YIG) changes the positive sign of the spin Hall magnetoresistance (SMR) in Pt/YIG to a negative sign at low temperature. Here, we use polarized neutron reflectometry to explore the coupling between NiO and YIG to understand the mechanism of the negative SMR. A weak uncompensated magnetic moment is observed in the NiO and the direction of this moment is perpendicular to YIG. Therefore, we infer that the spin axis of NiO is perpendicular to YIG. This result directly supports the explanation that the negative SMR results from the pure spin current reflected back by the NiO layer and the spin-flop coupling between NiO and YIG. [ABSTRACT FROM AUTHOR]

We report on an ultrahigh Hall mobility exceeding 40 000 cm2/V s and a very long traditional scattering time in a trivial layered semiconductor Bi2O2Se. Shubnikov-de Haas (SdH) oscillations were observed in both the unsaturated longitudinal linear magnetoresistance Rxx and the transverse Hall resistance Rxy. The amplitude ΔRxy of SdH oscillations was phase-shifted approximately 180° with respect to ΔRxx, indicating the strong suppression of electron backward scattering. This was further proved by the evidence of transport lifetime that is 10 times longer than the quantum lifetime. Our results show that the suppressed backward scattering in nontrivial Dirac semimetals can also occur in the trivial semiconductor Bi2O2Se. [ABSTRACT FROM AUTHOR]

The Ni40Co10−xFexMn33Al17 (x = 4, 6, 8) alloys are prepared by arc‐melting method. The crystallographic structure, magnetic and magnetoresistance properties are systematically studied. The large magnetic change is obtained across the martensitic transformation from the ferromagnetic austenite phase to weak‐magnetic martensite phase. With the increase in Fe/Co ratio, the martensite transformation temperature shifts to the lower temperature. The large values of magnetoresistance of 33.3, 25.7, and 13.1% are achieved at the field of 3 T for x = 4, x = 6, and x = 8 alloys around the martensitic transformation, respectively. These results indicate that Ni‐Fe‐Co‐Mn‐Al alloy provides the motive power for further research in practical applications. [ABSTRACT FROM AUTHOR]

The presence of thick buffer layers in magnetic sensor devices decreases sensor sensitivity due to shunt currents. With this motivation, we produced IrMn-based spin-valve multilayers without using buffer layer. We also studied the effects of post-annealing and IrMn thickness on exchange bias field (H EB ) and blocking temperature (T B ) of the system. Magnetization measurements indicate that both H EB and T B values are significantly enhanced with post-annealing of IrMn layer. In addition, we report that IrMn thickness of the system strongly influences the magnetization and transport characteristics of the spin-valve structures. We found that the minimum thickness of IrMn layer is 6 nm in order to achieve the lowest shunt current and high blocking temperature (>300 K). We also investigated the training of exchange bias to check the long-term durability of IrMn-based spin-valve structures for device applications. [ABSTRACT FROM AUTHOR]

We report the observation of the Hanle effect in the giant magnetoresistance measurement of metallic lateral nanostructures. By applying magnetic fields perpendicularly to the magnetization of the electrodes, we obtain resistance values lower than that of the parallel magnetization state, due to the extra decoherence provided by the random propagation time of the carriers. An analytical model is developed, enabling us to extract the characteristic transport parameters of CoFe, Al, and Cu from the fitting of the experimental results. We compare the obtained parameters to that of standard non-local Hanle measurements in lateral spin-valves, with the interest that this measurement configuration gives much larger signal variation. [ABSTRACT FROM AUTHOR]

We present an investigation of the hysteresis behavior of the magnetodielectric effect for Mn–Zn ferrite with different Zn doping. A noticeable magnetodielectric effect is observed in the ferrite samples. Both the magnetodielectric and magnetoresistance curves show similar magnetic field dependence and shape anisotropy. The hysteresis behavior of the magnetodielectric effect depends on the measuring frequency and Zn doping of the ferrite samples. Theoretical analysis suggests that the hysteresis behavior of the magnetodielectric effect results from the combination of magnetoresistance and magnetostriction effects. [ABSTRACT FROM AUTHOR]

We observe an unusual behavior of the low-temperature magnetoresistance of the high-mobility two-dimensional electron gas in InGaAs/InAlAs quantum wells in weak perpendicular magnetic fields. The observed magnetoresistance is qualitatively similar to that expected for the weak localization and antilocalization but its quantity exceeds significantly the scale of the quantum corrections. The calculations show that the obtained data can be explained by the classical effects in electron motion along the open orbits in a quasiperiodic potential relief manifested by the presence of ridges on the quantum well surface. [ABSTRACT FROM AUTHOR]

Abstract: Molecules are proposed to be an efficient medium to host spin‐polarized carriers, due to their weak spin relaxation mechanisms. While relatively long spin lifetimes are measured in molecular devices, the most promising route toward device functionalization is to use the chemical versatility of molecules to achieve a deterministic control and manipulation of the electron spin. Here, by combining magnetotransport experiments with element‐specific X‐ray absorption spectroscopy, this study shows the ability of molecules to modify spin‐dependent properties at the interface level via metal–molecule hybridization pathways. In particular, it is described how the formation of hybrid states determines the spin polarization at the relevant spin valve interfaces, allowing the control of macroscopic device parameters such as the sign and magnitude of the magnetoresistance. These results consolidate the application of the spinterface concept in a fully functional device platform. [ABSTRACT FROM AUTHOR]

Graphene and graphyne hold great potential for spintronic device applications due to their exceptionally good electrical and mechanical properties in the pristine form. Recently, considering these 2D carbon allotropes have similar bond lengths and unit cell shapes, ensuring a perfectly matched interface between them and construction of graphene/graphyne heterojunctions feasible. To this end, we study the spin-charge transport properties for monolayer graphene/graphyne zigzag-edged nanoribbon heterojunctions by employing the ab initio calculations, where two types of γ- and (6,6,12)-graphynes are considered, respectively. Our important result here is that these heterojunctions can exhibit an interesting variation of magnetoresistane by applying ferromagnetic stripes or external magnetic fields onto the ribbons to initially orient their spin configuration. Specifically, the magnetoresistance ratio can be up to 10 4 % for graphene/γ-graphyne heterojunction, but only 300% for the graphene/(6,6,12)-graphyne one. In addition, the effects of spin-filtering and negative differential resistance are also observed in those heterojunctions. The maximum of spin filtering efficiency can be up to 99%. The mechanisms are revealed and analyzed by the connection of these effects to the evolution of the spin-resolved electron transmission spectra and pathways around the Fermi level at zero bias. [ABSTRACT FROM AUTHOR]

We calculate the dielectric function of a system composed of a pair of electrically isolated Bernal graphene bilayers separated by a spacer as a function of temperature T , interlayer distance d and spacer dielectric constant ε 2 . Using the obtained results for dielectric function we calculate finite-temperature electrical conductivity of the first layer in presence of the second one due to the screened Coulomb scattering for different values of temperature, interlayer distance and dielectric constants ε 2 , ε 3 . [ABSTRACT FROM AUTHOR]

La 1−x Sr x Mn 0.5 Сo 0.5 O 3 (x ≤ 0.75) perovskites have been studied as a function of temperature by neutron powder diffraction (NPD), magnetization and magnetoresistance measurements. The NPD data show that x = 0.15 and 0.5 compounds are stoichiometric, so the Sr 2+ doping transforms Co 2+ ions into the Co 3+ ones, whereas manganese ions remain in the 4+ oxidation state as in the parent ferromagnetic compound LaCo 0.5 2 + Mn 0.5 4 + O 3 . The magnetization data show a decrease in the Curie temperature from 215 K for the compound with x = 0 down to 147 K for the compound with x = 0.05. The compounds with x > 0.15 show an increase in T C up to 260 K (x = 0.75) in spite of a gradual decrease of the spontaneous magnetization. The stoichiometric compound x = 0.5 demonstrates a sharp ferromagnet-paramagnet transition with T C = 250 K. However, there is no visible coherent magnetic contribution to the NPD patterns. All compounds are semiconductors and exhibit large magnetoresistance gradually increasing with decrease of temperature. The magnetic data have been interpreted assuming that the Co 3+ ions are in high spin state, however, there is a fraction of cobalt ions in low spin state. It is suggested that the superexchange interaction between Co 3+ ions in the high spin state and Mn 4+ ions is ferromagnetic and that the ferromagnetism of the compounds with x > 0.5 and high T C is associated with positive exchange interactions between Co 3+ being in high spin state and Mn 4+ ions distributed within the short range regions. Based on the NPD results and magnetization data the magnetic phase diagram has been constructed. [ABSTRACT FROM AUTHOR]

The non-stoichiometric ceramics are amazing materials with potential to offer applications that are unachievable by using otherwise ideal stoichiometric counterparts. These materials have contributed in wide areas including superconductivity, optical, magnetic, electronic, structural, mechanical and transport applications. The deviation form stoichiometry in a large number of compounds, though usually avoided, has numerous benefits; by increasing ionic conductivity, offering band structure modifications, causing paramagnetic to ferromagnetic transitions, reducing magnetoresistance, increasing mechanical strength, enhancing electrochemical efficiency etc. Keeping in mind the promising contributions of silicon carbide among family of ceramic materials, this review highlights the implications of non-stoichiometry and its properties. The non-stoichiometry produced unintentionally or purposefully is strongly influenced by synthesis conditions and varies for silicon carbide grown in amorphous, crystalline, polycrystalline polytypes in the form of bulk, surfaces and low dimensional structures. The prospects of tuning the properties of silicon carbide on the basis of fabrication of silicon rich and carbon rich by monitoring silicon to carbon ratio are discussed in detail. [ABSTRACT FROM AUTHOR]

A colossal positive magnetoresistive effect triggered by a laser was observed in a nonmagnetic Si-based metal-oxide-semiconductor structure. The positive magnetoresistance was greatly promoted compared to the case with no laser illumination. In addition, it shows high sensitivity to the magnetic field intensity above a certain threshold at room temperature, making it an appealing candidate for magnetic field detection. Moreover, the magnetoresistance can be regulated by the position of laser beams, which enables us to tailor the devices to meet various needs. We attribute this effect to the anisotropy of the carrier transport characteristics in our structure. The work suggests a different approach to develop laser-controlled magnetic devices and may greatly improve the performance of existing magnetoresistance-based devices. [ABSTRACT FROM AUTHOR]

This work investigates an eddy current-based non-destructive testing (NDT) method to characterize corrosion of pipes under thermal insulation, one of the leading failure mechanisms for insulated pipe infrastructure. Artificial defects were machined into the pipe surface to simulate the effect of corrosion wall loss. We show that by using a giant magnetoresistance (GMR) sensor array and a high current (300 A), single sinusoidal low frequency (5-200 Hz) pipe-encircling excitation scheme it is possible to quantify wall loss defects without removing the insulation or weather shield. An analysis of the magnetic field distribution and induced currents was undertaken using the finite element method (FEM) and analytical calculations. Simple algorithms to remove spurious measured field variations not associated with defects were developed and applied. The influence of an aluminium weather shield with discontinuities and dents was ascertained and found to be small for excitation frequency values below 40 Hz. The signal dependence on the defect dimensions was analysed in detail. The excitation frequency at which the maximum field amplitude change occurred increased linearly with the depth of the defect by about 3 Hz/mm defect depth. The change in magnetic field amplitude due to defects for sensors aligned in the azimuthal and radial directions were measured and found to be linearly dependent on the defect volume between 4400-30,800 mm3 with 1.2 × 10-3-1.6 × 10-3 μT/mm3. The results show that our approach is well suited for measuring wall loss defects similar to the defects from corrosion under insulation. [ABSTRACT FROM AUTHOR]

Group-IV-based ferromagnetic semiconductor Ge1- xFex (GeFe) is one of the most promising materials for spin injection/detection in Si and Ge. In this paper, we demonstrate a systematic study of tunneling magnetoresistance (TMR) in magnetic tunnel junctions (MTJs) composed of Fe/MgO/Ge1- xFex with various Fe concentrations (x = 0.065, 0.105, 0.140, and 0.175). With increasing x, the TMR ratio increases up to 1.5% when x ≤ 0.105, and it decreases when x > 0.105. This is the first observation of the TMR ratio over 1% in MTJs containing a group-IV ferromagnetic semiconductor. With increasing x, while the Curie temperature of GeFe increases, the MgO surface becomes rougher, which is thought to be the cause of the upper limit of the TMR ratio. The quality of the MgO layer on GeFe is an important factor for further improvement of TMR in Fe/MgO/GeFe MTJs. [ABSTRACT FROM AUTHOR]

A magnetoresistive sensor platform for the detection of individual magnetic reporter particles is presented. The sensing scheme is based on the detection of the shift in the sensor’s magnetoresistance-switching field in the presence of magnetic particle(s). A bottom-pinned spin-valve multilayer (Co/Ru/Co)/Cu/(Co/Ru/Co) device structure (with Ta/Ru seed and Ta capping layers) used for the sensor was deposited using ultra-high vacuum magnetron sputtering and patterned using conventional microfabrication techniques. Inexpensive electronics to measure device magnetoresistance (using DC currents) was used for testing. The detection of individual 500 nm Fe 3 O 4 nanoparticles as well as the detection of up to ten (10) nanoparticles was demonstrated and verified using scanning electron microscopy (SEM). The developed sensors are readily integratable into a biosensing platform for the detection of biomolecules at ultra-low concentration using magnetic nanoparticles as reporters. [ABSTRACT FROM AUTHOR]

Spin valve devices, consisting of a free magnetic layer, a spacer layer, and a pinned magnetic layer, are widely used in magnetic sensors and nonvolatile magnetic memories. However, even a slight bending deformation can affect the magnetization direction of the free magnetic layer, which will change the magnetoresistance signal of the devices. Therefore, it is a challenge to develop a flexible spin valve device with controllable performance. Here, an enhanced stress-invariance of the magnetization direction in amorphous CoFeB magnetic films on flexible polyimide substrates is achieved. The uniaxial anisotropy is induced by growing on the bent substrate under a magnetic field, which aligns more magnetic domains with easy axes along the direction perpendicular to the subsequently applied stress. Theoretical calculations indicate that pre-induced anisotropy with an easy axis perpendicular to the applied stress effectively resists the change in the magnetization direction during bending. These results are of importance for realizing better performance of flexible spin valve devices and the development of flexible spintronics. [ABSTRACT FROM AUTHOR]

We report the electrical (angular magneto-resistance and Hall), thermal (heat capacity) and spectroscopic (Raman, X-ray photoelectron, angle-resolved photoelectron) characterization of a bulk BiSe topological insulator, which was grown by self-flux method through solid-state reaction from high-temperature (950C) melt and slow cooling (2C/h) of constituent elements. BiSe exhibited metallic behaviour down to 5 K. Magneto-transport measurements revealed linear up to 400 and 30% magneto-resistance (MR) at 5 K under a 14-T field in perpendicular and parallel field directions, respectively. We noticed that the MR of BiSe is very sensitive to the angle of the applied field. The MR is maximum when the field is normal to the sample surface, while it is minimum when the field is parallel. The Hall coefficient ( R ) is seen nearly invariant with a negative carrier sign down to 5 K albeit having near-periodic oscillations above 100 K. The heat capacity ( C ) versus temperature plot is seen without any phase transitions down to 5 K and is well fitted ( C = γ T + β T ) at low temperature with a calculated Debye temperature ( 휃 ) value of 105.5 K. Clear Raman peaks are seen at 72, 131 and 177 cm corresponding to A $_{\mathrm {1g}}^{1}$ , E $_{\mathrm {g}}^{2}$ and A $_{1\mathrm {g}}^{2}$ , respectively. Though two distinct asymmetric characteristic peak shapes are seen for Bi 4f and Bi 4f, the Se 3d region is found to be broad, displaying the overlapping of spin-orbit components of the same. Angle-resolved photoemission spectroscopy (ARPES) data of BiSe revealed distinctly the bulk conduction bands (BCB), surface state (SS), Dirac point (DP) and bulk valence bands (BVB), and 3D bulk conduction signatures are clearly seen. Summarily, a host of physical properties for the as-grown BiSe crystal are reported here. [ABSTRACT FROM AUTHOR]

Persistent magnetoresistance effects in the phase-separated Pr0.65(Ca0.25Sr0.75)0.35MnO3/SrTiO3 and Pr0.65(Ca0.25Sr0.75)0.35MnO3/0.7PbMg1/3Nb2/3O3-0.3PbTiO3 heterostructures under a low magnetic field are investigated. It is observed that the persistent magnetoresistance effects decrease with increasing temperatures and the values for the heterostructures on 0.7Pb(Mg1/3Nb2/3) O3-0.3PbTiO3 and SrTiO3 substrates are about 86.6% and 33.2% at 40K, respectively. More interestingly, the applied electric field on the 0.7PbMg1/3Nb2/3O3-0.3PbTiO3 substrate can suppress the persistent magnetoresistance effect, indicating that different energy landscapes can be dramatically modulated by the piezo-strain. These results are discussed in terms of the strain-induced competition in the ferromagnetic state and the charge-ordering phase by the energy scenario, which provide a promising approach for designing devices of electric-magnetic memories in all-oxide heterostructures. [ABSTRACT FROM AUTHOR]

A SiO 2 -Co film with a Pt bottom electrode and an Au top electrode was deposited by magnetron sputtering at room temperature. The sample exhibits bipolar resistive switching properties. Both oxygen vacancies and Co nanoparticles in the SiO 2 -Co film contribute to resistive switching properties and the formation of conducting filaments. The sample, at high and low resistance states, exhibits magnetoresistance at 300 K and 10 K, respectively; this may be due to spin-dependent tunneling between Co particles through the SiO 2 barriers. Thus, the combination of resistive switching and magnetoresistance in a simple Pt/SiO 2 -Co/Au structure leads to the formation of multiple resistance states, which is promising for future applications of multiple-state non-volatile storage. [ABSTRACT FROM AUTHOR]

MgB samples are produced by ex situ reaction method under vacuum, and various (0, 10, 20 Bar) Ar pressure for 0.5 and 1 h. The effect of ambient pressure and annealing duration on the microstructure and electrical properties of bulk samples are investigated. XRD, SEM, and magnetoresistance measurements are made. The a and c lattice parameters and the grain size values are the highest for the samples produced under vacuum and their values decrease with increasing Ar pressure. Moreover, these values increase when the annealing duration increases from 0.5 to 1 h. The increasing pressure reduces the bond lengths between the atoms thus the grain sizes decrease. Smaller grain size promotes the connection between grains which results in an increase of the critical current density ( J ). SEM micrographs reveal that the produced samples have granular structure which is a characteristic feature of MgB. The decrease of grain sizes and thus enhancement in grain connectivity with increasing pressure is also confirmed by SEM images. Magneto resistivity measurements show that T values of the samples produced under vacuum are the highest. T values decrease with increasing ambient pressure and applied magnetic field. The activation energies ( U ) of the samples are calculated using Arrhenius plots due to thermally activated flux flow theory. Existence and increase of Ar pressure causes increase of activation energies. The samples produced with 0.5-h annealing have higher activation energies than the ones produced with 1-h annealing. [ABSTRACT FROM AUTHOR]