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arXiv 1609.06149cond-mat.mtrl-sci
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PrGe拓扑表面的巨Rashba效应揭示反铁磁自旋电子学

Giant Rashba effect at the topological surface of PrGe revealing antiferromagnetic spintronics

Soma Banik, Pranab Kumar Das, Azzedine Bendounan, Ivana Vobornik, A. Arya, Nathan Beaulieu, Jun Fujii, A. Thamizhavel, P. U. Sastry, A. K. Sinha, D. M. Phase, S. K. Deb

摘要:

磁性材料中的Rashba自旋轨道分裂为自旋电子学领域开辟了一个新的视角。本文报道了在PrGe [010]表面的顺磁相(Rashba系数α R= 5eV)中存在着巨大的Rashba型自旋轨道效应.电子能带结构的显着变化已被观察到的相变从顺磁到反铁磁(44 K)和从反铁磁到铁磁基态(41.5 K)。我们发现PrGe中的Pr 4f态在费米能级附近与Pr 5d和Ge 4s-4p态有很强的杂化。发现Rashba效应在k_x和k_y方向上的行为不同,分别表现为类电子带和类空穴带。在顺磁相中的Rashba效应的可能起源与该系统中存在的反平行自旋极化有关。第一性原理的密度泛函计算的Pr终止表面与反平行自旋显示出一个公平的协议与实验结果。我们发现,反平行自旋强耦合到晶格,使PrGe系统的行为类似于弱铁磁系统。对不同磁相的能量色散曲线的分析表明,在PrGe中存在着Dzyaloshinsky-Moriya相互作用和交换相互作用之间的竞争,从而导致了磁有序化. Dzyaloshinsky-Moriya相互作用的存在的支持证据被观察到的各向异性磁电阻相对于磁场方向和一阶型滞后的X射线衍射测量。在反铁磁相和可调的Rashba参数与温度跨越磁转变的巨大的负磁阻43%,使这种材料的技术应用在反铁磁自旋电子器件的合适的候选人。

英文摘要:

Rashba spin-orbit splitting in the magnetic materials opens up a new perspective in the field of spintronics. Here, we report a giant Rashba-type spin-orbit effect on PrGe [010] surface in the paramagnetic phase with Rashba coefficient α_R=5 eVÅ. Significant changes in the electronic band structure has been observed across the phase transitions from paramagnetic to antiferromagnetic (44 K) and from antiferromagnetic to the ferromagnetic ground state (41.5 K). We find that Pr 4f states in PrGe is strongly hybridized with the Pr 5d and Ge 4s-4p states near the Fermi level. The behavior of Rashba effect is found to be different in the k_x and the k_y directions showing electron-like and the hole-like bands, respectively. The possible origin of Rashba effect in the paramagnetic phase is related to the anti-parallel spin polarization present in this system. First-principles density functional calculations of Pr terminated surface with the anti-parallel spins shows a fair agreement with the experimental results. We find that the anti-parallel spins are strongly coupled to the lattice such that the PrGe system behaves like weak ferromagnetic system. Analysis of the energy dispersion curves at different magnetic phases showed that there is a competition between the Dzyaloshinsky-Moriya interaction and the exchange interaction which gives rise to the magnetic ordering in PrGe. Supporting evidences of the presence of Dzyaloshinsky-Moriya interaction are observed as anisotropic magnetoresistance with respect to field direction and first-order type hysteresis in the X-ray diffraction measurements. A giant negative magnetoresistance of 43% in the antiferromagnetic phase and tunable Rashba parameter with temperature across the magnetic transitions makes this material a suitable candidate for technological application in the antiferromagnetic spintronic devices.

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