正磁阻体系研究进展

近十几年来,磁致电阻效应及其机理的研究一直是凝聚态物理领域的研究热点之一。随着具有磁阻效应的各种新材料及新结构体系的合成、制备与发现,磁阻体系及其磁阻机制的复杂性也不断被展现出来。在已发现的各类磁阻体系及磁阻效应中,正磁阻体系及正磁阻效应的研究,作为磁阻研究的一个分支,在磁阻体系、磁阻机理和新型磁阻器件应用方面,均具有特殊的研究价值。本文综述了正磁阻体系、正磁阻效应及其磁阻机理的研究进展,展示了正磁阻体系、正磁阻效应及其机理的多样性,并简要指出了正磁阻体系研究中需要关注的一些共性问题。

高取向Fe_3O_4薄膜中织构诱导的自旋输运和磁化动力学

多晶材料的性能受到其晶粒群形貌及结构参数如晶粒取向分布函数的严重影响,这种影响在具有各向异性晶体结构的多晶薄膜以及多晶薄膜的电学性能方面表现得尤为突出,比较有代表性的例子就是Fe_3O_4磁性薄膜。作为一种典型的半金属,Fe_3O_4由于在费米面处理论上100%的自旋极化率以及适中的电阻率,成为半导体自旋电子学领域的热门材料。针对Fe_3O_4薄膜制备中经常出现的(111)取向生长模式,介绍了Fe_3O_4薄膜中织构结构相关的自旋输运及磁化动力学(磁各向异性)性能的研究进展。

Spin-Polarized Transport Through a Quantum Dot Coupled to Ferromagnetic Leads： Kondo Correlation Effect

We investigate the linear and nonlinear transport through a single level quantum dot connected to two ferromagnetic leads in Kondo regime, using the slave-boson mean-field approach for finite on-site Coulomb repulsion. We find that for antiparallel alignment of the spin orientations in the leads, a single zero-bias Kondo peak always appears in the voltage-dependent differential conductance with peak height going down to zero as the polarization grows to P = 1.For parallel configuration, with increasing polarization from zero, the Kondo peak descends and greatly widens with the appearance of shoulders, and finally splits into two peaks on both sides of the bias voltage around P ～ 0.7 until disappearing at even larger polarization strength. At any spin orientation angle θ, the linear conductance generally drops with growing polarization strength. For a given finite polarization, the minimum linear conductance always appears at θ = π.