Multiferroism in Pr2FeCrO6 perovskite

Pr₂FeCrO₆ perovskite crystallizes in an orthorhombic structure with R3c space group. Magnetic study has revealed that Pr₂FeCrO₆ exhibits room-temperature ferromagnetism with a Curie temperature of about 562 K. Pr₂FeCrO₆ also exhibits weak ferroelectricity. Thus, given its ferroelectric and ferromagnetic nature, the Pr₂FeCrO₆ material can be considered as a multiferroic. In addition, due to its high Curie temperature and multiferroicity, it could be a promising candidate for spintronics applications.     

Crossover of magnetoresistance from positive to negative in La0.5Sr0.5CoO3 − σ/Si heterostructure

The magnetoresistance (MR) properties of a heterostructure fabricated by depositing a La_0.5Sr_0.5CoO_3 − σ film on an n-type Si substrate have been studied. The heterostructure exhibits a good rectifying behavior. A negative MR at T = 210 K and a positive MR at T = 300 K are observed for all bias currents whereas; for temperatures ranging from 240 to 280 K the MR changes from being positive to negative with the increase of the bias current. The observed behavior of the MR effect is discussed in terms of current-induced ferromagnetic spin order.     

Rashba effect induced magnetoresistance in an InAs heterostructure

The Rashba field in a quantum channel produces spin splitting and population imbalance between spin-up and -down electrons. The channel resistance depends on the alignment between the applied field and the Rashba field because the applied magnetic field causes different mobilities for two types of spins. With an applied field of 2 T, the mobility difference between spin-up and -down electrons is 0.75%.     

Large magnetocaloric effect and magnetoresistance in ErNi single crystal

The magnetic properties,magnetocaloric effect and magnetoresistance in ErNi single crystal have been investigated in detail.With decreasing temperature,ErNi single crystal undergoes two successive mag-netic transitions:a paramagnetic to ferromagnetic transition at Tc=11 K and a spin-reorientation transition at TSR=5 K.Meanwhile,a sharp field-induced metamagnetic transition is observed below the Tc along the a axis.ErNi single crystal possesses a giant magnetocaloric effect around Tc.The maximum magnetic entropy change is-36.1 J(kg K)-1 along the a axis under the field change of 0-50 kOe.In par-ticular,the rotating magnetocaloric effect in ErNi single crystal reaches its maximum under a relatively low field,and the maximum rotating entropy change with a value of 9.3 J(kg K)-1 is obtained by rotat-ing the applied field from the[011]to[100]directions under 13 kOe.These results suggest that ErNi could be a promising candidate for magnetic refrigeration working at liquid-helium temperature region.Moreover,a complicated transport behavior is uncovered in ErNi single crystal,which is attributed to the complex magnetic states and magnetic polaronic effect.Both positive and negative magnetoresistance are observed.A considerable large magnetoresistance with the value of-34.5％is acquired at 8 K under 50 kOe when the field is along the[100]direction.     

Impact of the transition metal ion-doped on the electrical and magnetic properties of La0.67Ca0.33MnO3Ag0.15-based polycrystalline ceramics

In this work, high-quality La_0.67Ca_0.33MnO₃:Ag_0.15 and La_0.67Ca_0.33Mn_0.98B_0.02O₃:Ag_0.15 (B = Fe, Co, Ni) ceramics were prepared by the sol–gel route. The slight substitution of the Mn sites has significantly affected the metal–insulator transition and the ferromagnetic–paramagnetic transition. The Mn site doping leads also to a decrease in the temperature of the metal–insulator transition, an enhancement in resistivity, and a reduction in the saturation magnetization. More specifically, the Fe doping approach can significantly increase the peak temperature coefficient of resistance (TCR_peak), since the TCR_peak increases from 62.5%·K^?1 to 75.4%·K^?1. In addition, Fe, Co, and Ni doping can effectively elevate the peak magnetoresistance (MR_peak), of which the modification induced by Fe is the most significant since it enhances from 71.5% to 87.0%. Both the TCR_peak and MR_peak obtained are the highest in the current study, which can greatly promote the application of the manganate materials in the field of infrared detection and magnetic sensitivity.     

Effect of cold work on anisotropic magnetoresistance of Co25Ni75

Various states of the polycrystalline Co₂₅Ni₇₅ sample have been achieved by cold rolling and heat treatments after cold rolling. At each metallurgical stage, the electrical resistivity

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, measured in the saturated condition with a longitudinal field, and the resistivity

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, obtained under a similar condition with a transverse field, were studied at 77K. We used the quantity

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, defined as

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, where

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is the resistivity in zero field (or a demagnetized state), to check the magnetic anisotropy in the sample. It is found that cold work can induce an easy axis parallel to the roll direction. This phenomenon is associated with the short-range order and/or the directional Co–Co pair order formed during a cold-rolling process. Recovery and recrystallization were observed, if the rolled samples were annealed at various temperatures T_Q. Both stress relief and change of texturing lead to an enhancement of magnetic anisotropy of the longitudinal type. The anisotropic magnetoresistance

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of the cold-rolled sample (CR-0) is the lowest. When T_Q is increased,

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becomes recovered. However,

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of a plainly salt water quenched sample is always larger than that of a cold-rolled one.     

Structural,magnetic, and magnetotransport properties of LaFe0.5Ni0.5O3

The perovskite-type LaFe_0.5Ni_0.5O₃ belonging to the rhombohedral (space group R-3c) crystal structure has been synthesized for which we have identified a magnetic transition at T₁ =?8?K corresponding to the minimum observed in the derivative of temperature dependent magnetization. A bifurcation in the ZFC and FC curves is observed below T₁ that suggests a frustrated magnetic behavior. The non-zero moment above T₁ hints the possibility of the presence of a high-temperature magnetic transition in the material. The resistivity of LaFe_0.5Ni_0.5O₃ evolves as a function of temperature similar to that of a semiconductor. Mott's variable range hopping governs the conduction mechanism of the material. Presence of various anisotropy terms and inhomogeneous magnetic interactions lead to the presence of antiferromagnetic and ferromagnetic interfaces, which eventually causes a magnetic exchange bias and magnetic hysteresis in resistivity. We have also observed direction dependent magnetoresistance in the material.     

基于多采样频率的磁电阻效应测试方法研究

磁电阻效应特性曲线是一个具有脉冲特性的非线性曲线 ,在滤波和多采样频率间制定一个最优方案 ,可以改善磁电阻效应的测试。测量结果表明 ,该方法明显改善了磁电阻特性曲线 ,特别是在峰值或谷值附近 ,提高了对参数估计的精度     

Synthesis of Nd0.7Sr0.3MnO3 ceramics by high-energy ball milling

Strontium doped perovskite-type manganite Nd_0.7Sr_0.3MnO₃ is synthesized by high-energy ball milling. Nd_0.7Sr_0.3MnO₃ single phase with perovskite structure is formed completely after milling 4 h and the perovskite phase decreases gradually and changes into amorphous state with increasing ball milling time up to 12 h. The interesting point in this work is that the Nd_0.7Sr_0.3MnO₃ perovskite can be formed again from the amorphous with subsequent 6 h ball milling. In addition, the re-obtained perovskite seems to be more stable than Nd_0.7Sr_0.3MnO₃ compound prepared using solid-state reaction method.     

Electrical transport properties and room-temperature positive magnetoresistance of Fe3O4/a-C/n-Si junctions

Fe₃O₄/a-C/n-Si junctions were formed by sequent depositing a-C and Fe₃O₄ layers on Si substrates by facing-target magnetron sputtering. The junctions exhibit nonlinear and slightly asymmetric current-voltage behaviors. For the junctions with thinner a-C layers, high value of the ideality factors suggests that the current transport is primary dominated by thermionic field emission other than thermionic emission. The tunneling is found as the dominant mechanism for the junctions with thicker a-C layers. Compared to Fe₃O₄/n-Si junctions, the positive magnetoresistance in the Fe₃O₄/a-C/n-Si junctions was enhanced. Magnetoresistance is considered to originate from the interfacial scattering of carriers where the energy band of Fe₃O₄ is modified by the defect states. A possible mechanism for the enhancement of magnetoresistance is the heavier intermixing between Fe₃O₄ and a-C layer, which leads to a stronger scattering with the increase of a-C layer thickness.