Origin of the large positive magnetoresistance of Ge1－xMnx granular thin films
Origin of the large positive magnetoresistance of Ge1－xMnx granular thin films
复制标题
Ge1－xMnx颗粒薄膜大正磁阻的起源
DOI：
10.1103/physrevb.95.014417
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发表时间：
2017
影响因子：
3.7
通讯作者：
and S. Ohya
中科院分区：
文献类型：
--
作者：
Y. K. Wakabayashi;R. Akiyama;Y. Takeda;M. Horio;G. Shibata;S. Sakamoto;Y. Ban;Y. Saitoh;H. Yamagami;A. Fujimori;M. Tanaka;and S. Ohya
(GeMn)颗粒薄膜具有较大的正磁阻(MR)，是一种独特的自旋电子应用材料。以前对GeMn的研究表明，大的磁阻与GeMn的纳米旋节分解为富锰的铁磁纳米颗粒和贫锰的顺磁基质有关。然而，MR的微观起源尚不清楚。在这里，我们开发了一种方法来分别研究纳米颗粒和基质的磁性，利用X射线磁性圆二色谱(XMCD)对每个原子的局域磁态的极高敏感性。我们发现，磁阻比与纳米颗粒和基质产生的磁化强度的乘积成正比。这一结果表明，纳米粒子中的自旋极化空穴穿透到基质中，这些空穴经历了基质中顺磁性锰原子的一级磁散射，从而产生了大的磁阻。
(GeMn) granular thin films are a unique and promising material for spintronic applications owing to their large positive magnetoresistance (MR). Previous studies of GeMn have suggested that the large MR is related to the nanospinodal decomposition of GeMn into Mn-rich ferromagnetic nanoparticles and a Mn-poor paramagnetic matrix. However, the microscopic origin of the MR has not yet been clarified. Here, we develop a method to separately investigate the magnetic properties of the nanoparticles and the matrix, utilizing the extremely high sensitivity of x-ray magnetic circular dichroism (XMCD) to the local magnetic state of each atom. We find that the MR ratio is proportional to the product of the magnetizations originating from the nanoparticles and the matrix. This result indicates that the spin-polarized holes in the nanoparticles penetrate into the matrix and that these holes undergo first order magnetic scattering by the paramagnetic Mn atoms in the matrix, which induces the large MR.