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(100- x) Sr0.7La0.3Fe11.75Co0.25O19–(x) CoFe2O4 composites were synthesized by the one pot sol–gel auto-combustion method. The individual phase purity, morphology, and magnetic hysteresis loop of the composite magnet were analyzed by x-ray powder diffraction, field emission scanning electron microscopy and vibrating sample magnetometer, respectively. The apparent observation of the room temperature hysteresis loop indicates the existence of interfacial exchange interactions. Nevertheless, saturation magnetization (Ms) follows the trend of Vegard's law. The nature of magnetic interaction and its dependency on the amount of each phase were analyzed by employing the Thamm–Hesse plot. The critical size of the soft phase particle did not corroborate with the results of Δ M v s H plot. However, this synthesis method is found to be successful in obtaining single-step magnetization reversal in hard–soft composite magnets. The deviation from ideal non-interacting Stoner–Wohlfarth particles puts the single hard phase into the limelight. The (BH)max in the range of 1.07–0.98 MGOe has been obtained for the synthesized composite magnet. [ABSTRACT FROM AUTHOR]

In the current study, we developed a simple and biocompatible method for producing core–shell nanoparticles (NPs). Citrate auto combustion and green procedures were used to create core–shell Ag/CoGd0.025Er0.05Fe1.925O4 (Ag/CGEFO) sample with an average crystallite size of 26.84 nm. The prepared samples were characterized via different structural techniques, such as x-ray diffraction (XRD), Raman Spectroscopy (RS), High-Resolution Transmission Electron Microscopy, and Energy Dispersive x-ray analysis. These analyses were utilized to characterize and confirm the successful formation of the core–shell architecture. For core–shell NPs, all peaks of Ag and CGEFO ferrite are detected in the XRD, confirming the co-presence of the ferrite spinel phase and the cubic Ag phase. The magnetic hysteresis curves demonstrate typical hard ferri-magnetic behavior along with maximum magnetic saturation values up to 53.74 emu g−1 for the CGEFO sample, while an enhanced coercivity is detected for the coated sample. Moreover, the width of the hysteresis loop is increased for the Ag/CGEFO sample compared to the uncoated one. This indicates that the addition of Ag as a shell increases magneto crystalline anisotropy. Moreover, the E g of uncoated CGEFO is equal to 1.4 eV, increasing to 3.6 eV for coated ones. This implies the influence of CGEFO is diminished when the surface is coated with Ag (shell), and the reflectance of the Ag/CGEFO core–shell is nearly dependent on the reflectance of the Ag shell layer. Consequently, the Ag/CGEFO can be used as a light shielding substance. [ABSTRACT FROM AUTHOR]

Fe 1 + y Te0.6Se0.4 has considerable application potential due to its large critical current density (J c) and high upper critical magnetic field ( H c2 ). However, the uncertainty of the anisotropy of J c and the unclear flux-pinning mechanism have limited the application of this material. In this study, the J c in three directions were obtained from magnetic hysteresis loop measurements. A large anisotropy of J c a b / J c c ∼ 10 was observed, and the origin of the anisotropy was discussed in details. Flux pinning force densities (F p) were obtained from J c, and a non-scaling behavior was found in the normalized pinning force f p [ F p / F p-max ] versus the normalized field h [ H / H c2 ]. The peaks of pinning force shift from a high h to a low h with increasing temperature. Based on the vortex dynamics analysis, the peak shift was found to originate from the magnetization relaxation. The J c and F p at critical states free from the magnetic relaxation were regained. According to the Dew-Hughes model, the dominant pinning type in Fe 1 + y Te0.6Se0.4 clean single crystals was confirmed to be normal point pinning. [ABSTRACT FROM AUTHOR]

La2NiMnO6—a ferromagnetic (FM) insulator offers tunable charge carriers and spins useful to devise its multiple properties and applications. In this view, we studied a core-shell La2NiMnO6 (2–3 nm shell on 65 – 80 nm core) of a Ni2+/Ni3+(d7) to Mn4+/Mn3+ (d4) spin-up conversion— revived a new FM phase-2, raising a spin-density σs = 0.7 s a−1 over the Ni2+/Mn4+ species (phase-1), σs = 0.5 s a−1, i.e. 2.12 μB/f.u. larger spin moment. HRTEM images studied with x-ray diffraction characterizing core-shell structure that plays a crucial role in tuning the high spin FM phase-2 of profound properties. Below 110 K, the dc magnetization and ac magnetic susceptibility χ(ω, T) reveal a metastable magnetic behavior on an antiferromagnetic canting of a spin-glass nature. The results follow a Vogel–Fulcher type relaxation with a relaxation time τ0 ∼ 10−13 s, confirming a spin-glass freezing behavior. Uniquely, FM field of phase-1 controls magnetics of phase 2 of a coupled magnet, modulating joint features with small thermal magnetic hysteresis on heating-cooling cycles. [ABSTRACT FROM AUTHOR]

The effects of wheel speeds and high-pressure hydrogen treatment on phase evolution, microstructure, and magnetocaloric properties in La0.5Pr0.5Fe11.4Si1.6 melt-spun ribbons are studied in this work. The results reveal that the increase of wheel speed is beneficial to the formation of cubic NaZn13-type phase and the grain refinement. The optimized wheel speed for microstructural and magnetocaloric properties is 30 m/s. The largest entropy change of 18.1 J/kg⋅K at 190 K under a magnetic field change of 0 T–5 T is obtained in La0.5Pr0.5Fe11.4Si1.6 ribbons melt-spun at 30 m/s. After a high-pressure hydrogen treatment of 50 MPa, the Curie temperature of the ribbons prepared at 30 m/s is adjusted to about 314 K and the large –ΔSM of 17.9 J/kg⋅K under a magnetic field change of 0 T–5 T is achieved at room temperature with almost none hysteresis loss. The small thermal and magnetic hysteresis and the large –ΔSM make the La0.5Pr0.5Fe11.4Si1.6 hydride ribbons appropriate for magnetic refrigerant applications around room temperature. [ABSTRACT FROM AUTHOR]

The in-plane effective 90° magnetization rotation of Co2FeAl thin film grown on PMN-PT substrate induced by the electric field is investigated at room temperature. The magnetic hysteresis loops under different positive and negative electric fields are obtained, which reveals remanent magnetization can be mediated by the electric field. Moreover, under positive electric fields, the obvious 90° magnetization rotation can be observed, while remanent magnetization is nearly unchanged under negative electric fields. The result is consistent with the electric field dependence of effective magnetic field, which can be attributed to the piezostrain effect in Co2FeAl/PMN-PT structure. In addition, the piezostrain-mediated 90° magnetization rotation can be demonstrated by the result of resonance field changing with electric field in the measurement of ferromagnetic resonance, which is promising for the design of future multiferroic devices. [ABSTRACT FROM AUTHOR]

The effect of Co addition on magnetic hysteresis, martensitic transformation temperature, and magnetic entropy change of rapidly-quenched Mn50−xCoxNi40In10 alloy nanomaterials has been investigated. The melt-spun Mn50Ni40In10 sample exhibits a small magnetic hysteresis which is further reduced by Co doping as measured between 0 and 2 T. The martensitic transformation temperature increases linearly with the electron concentration in the alloy from 195 K for Mn50Ni40In10 to 378 K for Mn45Co5Ni40In10. The Mn47Co3Ni40In10 alloy, which has phase-transition temperature close to room temperature, exhibits a substantial peak entropy change of 29.7 J kg−1 K−1 at magnetic field change of 2 T. Our results demonstrate that Mn47Co3Ni40In10 nanomaterial exhibits promising magnetocaloric properties for near-room-temperature magnetic refrigeration. [ABSTRACT FROM AUTHOR]

In the present work, the microstructure evolution and macro-response of a ferromagnetic shape memory alloy under stimuli of magnetic fields with different frequency and coupled magnetic-mechanical loading are investigated via a real-space phase field simulation. It is found that the coercive field is reduced from 0.724 to 0.423 with the magnetic frequency f decrease from Hz to Hz, wherein the concomitant domain wall motion and magnetization rotation are captured as well. Moreover, simulation results demonstrate that, under the coupled magnetic-mechanical loading, the coercive field of the magnetic hysteresis loop could be reduced by applying a compressive strain perpendicular to the magnetic field direction. The domain evolution is mainly divided into three types during the coupled magnetic-mechanical loading, namely (a) domain wall motion with the magnetization rotation, (b) pure magnetization rotation, and (c) 180° domain coordinated domain switching. To better understand the domain evolution, we propose an index , with and indicating the absolute value of the averaged magnetization component and over the whole studied system, to characterize the magnetization change during the microstructure evolution. [ABSTRACT FROM AUTHOR]

We propose a combination of the Kolmogorov–Johnson–Mehl–Avrami nucleation and growth theory and the Bean–Rodbell model to describe the field-induced transition in LaFe11.6Si1.4 alloys. The approach is applied to a set of bulk samples undergoing first-order transitions produced by different routes and including doping effects. The kinetic analysis of both magnetization and demagnetization processes reveals a nucleation and three-dimensional interface-controlled growth for these alloys. Introducing the kinetic process between the metastable and stable solutions of the Bean–Rodbell model, the field dependence of the magnetization/demagnetization processes, including magnetic hysteresis for different magnetic field sweeping rates, is better reproduced than with the pure model. [ABSTRACT FROM AUTHOR]

Epitaxial FeSi film on MgO (001) substrate was fabricated via a radio frequency magnetron sputtering technology. The epitaxial relationship of FeSi(001)/[110]//MgO(001)/[100] was characterized by crystal structure measurements and confirmed by in-plane biaxial magnetic anisotropy through vibrating sample magnetometer (VSM). By measuring Kerr magnetic hysteresis loops and recording the real-time magnetic domain images through surface magneto-optic Kerr effect (MOKE), two successive 90° domain wall displacement along easy axis and two discontinuous 90° domain wall displacement along hard axis were directly observed. Meanwhile, the difference of magnetic hysteresis loops obtained by VSM and MOKE devices were discussed. Furthermore, from the results of magnetic field sweeping ferromagnetic resonance measurements, it was found that FeSi film possesses an anisotropic effective damping constant of 0.0042 for easy axis direction and 0.0053 for hard axis direction, which was ascribed to the crystallographic defects induced two magnon scattering contributions. [ABSTRACT FROM AUTHOR]

The structural phase transformation in a non-stoichiometric shape memory Fe42.8Mn27.6Ga29.6 Heusler glass-coated microwire was experimentally observed using indirect magnetic, permeability, and electrical resistance measurements. While the temperature dependence of magnetization revealed hysteresis of magnetization during the heating and cooling process, magnetic hysteresis loops point to the change in the direction of the easy magnetization axis of the low- and high-temperature phase. Additionally, the unusual behavior of the permeability and electrical resistance measurements are in good agreement with the magnetic measurements. The x-ray diffraction profile measured at room temperature revealed the coexistence of a high-temperature L21 phase (a = 5.88 Ă...) and low-temperature phase with the L12 structure (a = 3.71 Ă...) and can be considered as another proof of the shape memory effect that is expected in the Feâ€"Mnâ€"Ga-based Heusler alloys. In the presented glass-coated microwire, it is not only possible to shift the transformation temperature with the external magnetic field, but from its initial permeability value, it is possible to determine whether the alloy has undergone the structural transformation. Therefore, the presented Feâ€"Mnâ€"Ga-based glass-coated microwire may be considered a suitable candidate for microactuators with sensory capabilities. [ABSTRACT FROM AUTHOR]

The acrylamide polymer gel template method has been adopted to synthesize single phase Dy1–xGdxMnO3 (DGMO, x= 0, 0.05, 0.1, 0.15, 0.2) ceramics. The Rietveld refinement of x-ray diffraction patterns recorded at room temperature suggests that DGMO ceramics are stabilized in an orthorhombic crystal structure with a Pnma space group. Gd3+ cations play an important role in stabilizing the orthorhombic phase and the unit cell volume increases with x. We report the phonon spectra of pure and Gd-substituted DyMnO3 (DMO) and their mode assignments. Raman modes are softened with x due to the relaxation in the stiffness constants upon the increase in the volume of the unit cell. The magnetic transition temperatures corresponding to TN(Dy) and Tlock decrease with the increase in Gd concentration as inferred from the temperature dependent magnetization data (M–T curve). The magnetization value increases below TN(Dy) with the increase in the Gd concentration as observed from the M–T plot. The magnetic hysteresis loop is fitted to extract ferromagnetic and antiferromagnetic/paramagnetic contributions for each composition x. Fittings of M–H loops indicate the increase in the magnetic contribution below TN(Dy) upon increasing the Gd dopant concentrations, while that decreases above TN(Dy). The temperature dependent specific heat data identifies these magnetic transition temperatures TN(Dy), Tlock and TN(Mn). Furthermore, magnetic field dependencies on TN(Dy), Tlock and TN(Mn) are studied in an elaborate manner. Both DMO and DGMO samples are found to be viable candidates for magnetic refrigeration applications in cryogenic temperature region. [ABSTRACT FROM AUTHOR]

The double perovskite La2FeMnO6 is ideally expected to be a ferrimagnet with a low saturation moment of 1 μB/f.u. Inhomogeneity in the Fe/Mn sites, along with other lattice disorders, can modify the exchange interactions in the material and result in a net saturation moment of more than 1 μB/f.u. Here, the origin of complicated magnetic behavior is examined of a pure phase La2FeMnO6 sample prepared by the sol-gel method. XRD analysis established that the material crystallizes in the orthorhombic Pbnm symmetry. The comprehensive analysis of x-ray photoelectron spectroscopy, x-ray near edge structure, and magnetic measurements acknowledge an antiferromagnetic coupling between Fe3+ and Mn3+ cations, thereby, resulting in the ferrimagnetic ground state for La2FeMnO6. The magnetic hysteresis loop obtained at 5 K shows a large coercivity of ∼820 Oe and a saturation moment of 1.6 μB/f.u., hinting at partial B-site ordering in La2FeMnO6. The ac susceptibility and dc magnetization measurements indicate the existence of magnetic glassy states (of cluster-glass type) with two distinct dynamical freezing points at ∼27 and 92 K, along with a Griffiths-like phase in the material. The experimental results are discussed taking several possible exchange interactions among Fe3+ and Mn3+ ions in the system into consideration. The magnetic complexity of this system makes it attractive for fundamental research and technological applications. [ABSTRACT FROM AUTHOR]

Understanding the mechanisms that limit the current transport in granular iron-based superconductors is necessary to unlock their potential for magnet applications. This paper reports the transport critical current surface IC(T,H) of powder-in-tube Ag/Ba1−xKxFe2As2 tapes densified by flat rolling and uniaxial hot pressing. We investigate the amplitude of the isothermal-IC(H)-curve magnetic hysteresis, which is a marker for the electrical connectivity between superconducting grains. This allows us to demonstrate that, in spite of an improved connectivity, the percolative path through weakly linked grains continues to play a role in the IC properties of hot-pressed conductors. The limitations to the current transport due to weak links depend on the orientation of the magnetic field and are more severe when H is on the tape plane. This finding provides a justification to the puzzling evidence that IC(H) can be smaller for magnetic fields applied on the tape plane and not perpendicular to it. Finally, we report an unexpected increase of IC upon augmenting the magnetic field from 0 to ∼2 T. SQUID measurements reveal a superparamagnetic-like magnetic background that takes place in the same range of magnetic fields. A microscopic study of the conductor-core elemental composition provides evidences that these features can be both related to the presence of Fe-rich non-stoichiometric regions in the superconducting core. On a more general note, this study points out that further advances in the in-field current transport properties of powder-in-tube Ag/Ba1−xKxFe2As2 conductors are possible and rely to a large extent on solutions to improve the inter-grain connectivity and the quality of the superconducting phase. [ABSTRACT FROM AUTHOR]

When exposed to time-dependent magnetic fields, REBCO Roebel cables generate AC loss resulting from both magnetic hysteresis and induced inter-strand coupling currents. Until now, the AC loss has been computed in a two-dimensional approximation assuming fully coupled or decoupled strands, and a finite inter-strand resistance could be simulated only with three-dimensional models. In this work, we propose a homogenization procedure that reduces the three-dimensional geometry of the Roebel cable to two dimensions, without ignoring connections between the strands. The homogenized cable consists of two parallel 'monoblocks' with an anisotropic resistivity. The proposed model enables computation of AC coupling loss without the need for complex three-dimensional simulations. For experimental validation, a Roebel cable with soldered strands was prepared. The inter-strand resistance was determined by applying a transverse current and measuring the voltage profile. Additionally, the AC magnetization loss of the cable was measured in fields of 1 to 50 mT with frequencies of 1 to 2048 Hz using a calibration-free technique. With the measured inter-strand resistance as input parameter, the monoblock model gives a good estimate for the AC loss, even for conditions in which the coupling loss is dominant. [ABSTRACT FROM AUTHOR]

This article reports exchange bias (EB) in nanocrystalline cobalt chromite CoCr2O4, - a phenomenon manifested by loop shift followed by increase in coercivity after cooling the sample in static magnetic field. The average particle size of the nanocrystalline CoCr2O4 is 30 nm, confirmed from transmission electron microscopy images. Thermal variation of magnetization data M(T), in zero field cooling (ZFC) and field cooling (FC) modes depict long range order below the lock-in transition at TL≈16 K, spin-spiral transition at TS≈28 K and a collinear ferrimagnetic state at TC≈100 K. Magnetic hysteresis loops are recorded in ZFC and FC modes at different cooling fields (). In addition, hysteresis loops are recorded in FC mode for a wide temperature range. In both cases, a clear signature of conventional exchange bias effect is observed. Analysis of the training effect in magnetic hysteresis loop and temperature dependent ac susceptibility (χac) at different frequencies suggest that the surface spins of CoCr2O4 nanoparticles play an important role in controlling the magnetic properties, and enhance the EB effect in collaboration with competition between non-collinear spiral spin state and collinear long range ferrimagnetic order. [ABSTRACT FROM AUTHOR]

This article reports exchange bias (EB) in nanocrystalline cobalt chromite CoCr2O4, - a phenomenon manifested by loop shift followed by increase in coercivity after cooling the sample in static magnetic field. The average particle size of the nanocrystalline CoCr2O4 is 30 nm, confirmed from transmission electron microscopy images. Thermal variation of magnetization data M(T), in zero field cooling (ZFC) and field cooling (FC) modes depict long range order below the lock-in transition at TL≈16 K, spin-spiral transition at TS≈28 K and a collinear ferrimagnetic state at TC≈100 K. Magnetic hysteresis loops are recorded in ZFC and FC modes at different cooling fields (). In addition, hysteresis loops are recorded in FC mode for a wide temperature range. In both cases, a clear signature of conventional exchange bias effect is observed. Analysis of the training effect in magnetic hysteresis loop and temperature dependent ac susceptibility (χac) at different frequencies suggest that the surface spins of CoCr2O4 nanoparticles play an important role in controlling the magnetic properties, and enhance the EB effect in collaboration with competition between non-collinear spiral spin state and collinear long range ferrimagnetic order. [ABSTRACT FROM AUTHOR]

We present theoretical results when applying the Cartesian product of two Kuramoto models on different network topologies. By a detailed mathematical analysis, we prove that the dynamics on the Cartesian product graph can be described by the canonical equations as the Kuramoto model.We show that the order parameter of the Cartesian product is the product of the order parameters of the factors.On the product graph, we observe either continuous or discontinuous synchronization transitions. In addition, under certain conditions, the transition from an initially incoherent state to a coherent one is discontinuous, while the transition from a coherent state to an incoherent one is continuous, presenting a mixture state of first and second order synchronization transitions. Our numerical results are in a good agreement with the theoretical predictions. These results provide new insight for network design and synchronization control. [ABSTRACT FROM AUTHOR]

Significant new functionality is reported for torsion mechanical tools aimed at full magnetic characterizations of both spin statics and dynamics in micro- and nanostructures. Specifically, two orthogonal torque directions are monitored and the results co-analyzed to separate magnetic moment and magnetic susceptibility contributions to torque, as is desired for characterization of anisotropic three-dimensional structures. The approach is demonstrated through application to shape and microstructural disorder-induced magnetic anisotropies in lithographically patterned permalloy, and will have utility for the determination of important magnetic thin-film and multilayer properties including interface anisotropy and exchange bias. The results reflect remarkable sensitivity of the out-of-plane magnetic torque to the nature of small edge domains perpendicular to the applied field direction, and also contain tantalizing indications of direct coupling to spin dynamics at the frequency of the mechanics.

As a model of second-generation high-temperature superconducting (2G HTS) power transmission cable, the effect of soft ferromagnetic (FM) substrate on hysteretic ac loss in a round cable carrying transport current or exposed to radial magnetic field is investigated theoretically. We consider the FM substrates as ideal soft magnets with an infinite permeability, neglecting the magnetic hysteresis. The analytical expressions of field and current distribution around a curved superconductor tape with FM substrate were derived applying the complex-field approach. FM components can strongly influence the ac loss behaviors in a round cable composed of coated conductors. The approximate expressions for ac loss in a round cable at small currents or low fields are obtained. It is shown that at small currents the ac loss QFM in a round cable for FM substrate depended on ac current amplitude ia and central angle θn as , while at low fields ha , the order of which differs significantly from QNM for nonmagnetic (NM) substrate. Additionally, the influence of the central angle as well as tape-width of coated conductors on the ac loss characteristic in a round cable is discussed. The ac loss QFM can be reduced by a suitable tape-width of coated conductor at higher fields as compared with QNM. [ABSTRACT FROM AUTHOR]

Bulk ceramic compounds of formula xPZT + (1 − x)PFW, where PZT = Pb(Zr0.575Ti0.425)O3 and PFW = Pb(Fe2/3W1/3)O3, for x = 0.15; 0.20; 0.25; 0.37; 0.50; 0.60; 0.65; 0.70 and 0.80, were synthesized. In these single phase perovskites a change from rhombohedral to cubic structure is observed as the proportion of PFW increases. Magnetic investigations including zero-field cooled and field-cooled magnetization versus temperature measurements, magnetic hysteresis loops measurement and ac susceptibility measurements were performed. At high temperatures a clear antiferromagnetic (AFM)-like transition was observed for high PFW concentrations. The low temperature behaviour indicated spin freezing and thermal activation of magnetic moments and measurements confirmed the existence of a barrier maximum for x = 0.37. Competition between the long-range AFM order and short-range magnetic ordering of small nano-sized regions with finite magnetic moments was observed in the studied system. [ABSTRACT FROM AUTHOR]

We report the effects of thickness of spacer layers and temperature on the magnetic properties of multilayer structured [FeTaC(50 nm)/Ta(x nm)]n=3/FeTaC(50 nm)/substrate amorphous thin films. A transcritical loop with a large coercivity (HC) of 25 Oe was observed for x = 0 film, but the loop shape was changed to flat loop along with a rapid decrease in HC (<0.25 Oe) by introducing Ta spacer layers. This is attributed to loss of perpendicular anisotropy causing a transition from stripe domain structure to in-plane orientation of spins. Magnetic hysteresis loops measured at different temperatures exhibited a spacer layers' thickness dependent multistep magnetization reversal processes for temperature below 80 K. Thermo- magnetization curves obtained under zero-field-cooled and field-cooled conditions displayed a bifurcation between them for x = 0 film. However, the bifurcation point was shifted to lower temperatures with increasing x and disappeared eventually for films with x ⩾ 4. High-temperature magnetization data revealed no significant changes in the magnetic properties up to Curie temperature. The observed results are elucidated on the basis of change in magnetic structure with the thickness of the spacer layers, pinhole effects at the interface, and temperature, instigating an effective reduction in perpendicular anisotropy and magnetic disorder, and thereby enhancing magnetic properties in multilayer thin films. [ABSTRACT FROM AUTHOR]

We report on the superconducting state of Ti0.8V0.2 alloy, highlighting an anomalous magnetic response in the flux-line lattice or the mixed state. The value of magnetization while cooling down the alloy in the presence of high magnetic field is lower than that obtained while warming it up from the lowest temperature in the presence of the same magnetic field. This is just the opposite to the thermo-magnetic hysteresis observed due to homogeneous flux-line pinning. This anomalous effect appears below a characteristic temperature that shifts towards a lower temperature with the increase in applied magnetic field. The value of magnetization measured at a constant temperature after cooling down the sample in the presence of magnetic field increases appreciably with time in the temperature–field domain where this anomalous effect is observed. These results indicate that the present Ti0.8V0.2 alloy exhibits a high field paramagnetic effect resulting from inhomogeneous flux pinning. Optical metallography and x-ray diffraction measurements show the formation of stress induced martensitic phase in the alloy, which could result in the inhomogeneous flux pinning. The temperature dependence of magnetization after annealing the sample after mechanical processing showed the usual properties of a type-II superconductor. This supports the argument that the inhomogeneous distribution of the stress induced martensitic phase is the reason for the existence of the high field paramagnetic effect in Ti0.8V0.2 alloy. [ABSTRACT FROM AUTHOR]

Structural and magnetic phase transitions of Mn-rich Mn50.5−xNi41Sn8.5+x (x = 0, 1 and 2) alloys were studied by magnetic and electrical measurements. The shift in martensitic transition temperature was less sensitive to the Mn/Sn ratio as compared to the Ni/Sn ratio. A magnetic entropy change (ΔSM) ∼ 11.85 J kg−1 K−1 was obtained for x = 0 at 270 K due to a change in magnetic field ΔH of only 1.5 T. Incorporating hysteresis losses, the net refrigerant capacity was estimated to be 44.82 J kg−1 for the same sample, which was found to be larger than that of other reported Ni-rich Ni–Mn–Sn alloys. Nearly 33% magnetoresistance was achieved for these alloys in presence of 8 T field differences. [ABSTRACT FROM AUTHOR]

We report on the role that oxygen vacancies have in determining the magnetic properties of Cu-doped ZnO. The observed magnetic hysteresis and the temperature dependence (irreversibility) of magnetization behave like supermoments blocked along random directions for a low-temperature annealed sample. The magnetic hysteresis (finite coercivity and low field saturation) and the irreversibility of temperature-dependent magnetization are destroyed upon thermal annealing. We propose that oxygen vacancies play an important role in inducing supermoments to explain the observations. [ABSTRACT FROM AUTHOR]

The full-optical set-up snap-shot Mueller matrix polarimeter (SMMP) is used to measure the channelled spectrum Iλ(λ) related to a twisted ferroelectric liquid crystal (TwFLC) studied here with this technique. The samples were preliminarily exposed to a high-amplitude/low-frequency rectangular voltage before all the optical measurements. This voltage applied permits one to work in the specific stripe regime. From the channelled spectrum recorded Iλ(λ), the different Mueller matrix (MM) can be obtained: the depolarization matrix, the retardance matrix and the diattenuation matrix. Several scalar polarimetric parameters are extracted from these MM, and especially αR(t), ϵR(t) and R(t). These relevant scalar coefficients, calculated from the retardance matrix, are used to determine the three hysteresis loops αR(V ), ϵR(V ) and R(V ). We define ψ as the difference of angle between the two rubbing directions of the two symmetrical (top and bottom) substrates and we examine how the hysteresis loops obtained are modified with the value of the geometrical externally controllable parameter ψ, for angles between ψ = 0°? and ψ = 90°. The key characteristics of the hysteresis loops and the evolution of these key values with ψ are detailed. [ABSTRACT FROM AUTHOR]