Co/Pt多层膜反常霍尔效应中周期性振荡机理研究

Co/Pt multilayers with perpendicular magnetic anisotropy have attracted wide attentions for potential applications in high-density perpendicular magnetic recording because of their high coercivity, moderate Curie temperature and high remanence ratio.Recently, due to the development of spintronics, more and more attentions have focused on magnetotransport property- - the extraordinary Hall effect (EHE) in these classes of materials. In magnetic multilayers, the interface scattering and bulk scattering contribute to the EHE in a different way. Researches show that the EHE can be effectively amplified by metal/metal interface and insulator/metal interface in the Co/Pt multilayers. However, the control mechnism of interface scattering for EHE will be further improved. Via replacing the Pt capping layer by the antiferromagnetic CoO layer and manipulating the configuration of the Co/Pt multilayers, this subject should investigate systematically the effect of the interface scattering on the magnetic and transport properties of the Co/Pt multialyers, and investigate periodic oscillation mechanism of extraordinary Hall effect in the Co/Pt multilayers.This research can encrich the theory of transport property, and provide theoretical basis for applications of the magnetic multialyers with perpendicular anisotropy such as the Co/Pt multialyers in high-sensitivity EHE sensors.

垂直磁各向异性的Co/Pt多层膜具有高矫顽力、适中的居里温度和高剩磁比等优良特性，在高密度垂直磁记录中得到广泛应用。近来，由于自旋电子学的兴起，人们越来越关注这类材料的磁输运特性- - 反常霍尔效应。在磁性多层膜中，体散射和界面散射对反常霍尔效应的贡献是不同的。研究表明金属/金属界面和金属/绝缘体界面均可以有效地增强Co/Pt多层膜的反常霍尔效应。然而，界面散射对反常霍尔效应的调控机制仍需要进一步的完善。我们将采用反铁磁CoO层取代Pt保护层、Co/Pt多层膜结构调整等途径，系统研究界面散射对Co/Pt多层膜磁学和输运特性的影响，探讨反常霍尔效应周期性振荡的机理。本项目研究成果可以丰富Co/Pt多层膜的输运理论，为Co/Pt等多层膜在高灵敏度的霍尔效应传感器中的开发应用奠定理论基础。

垂直磁各向异性的Co/Pt多层膜具有高矫顽力、适中的居里温度和高剩磁比等优良特性，在高密度垂直磁记录中得到广泛应用。本项目系统调控Co/Pt多层膜的厚度和周期数，发现Co/Pt多层膜反常霍尔效应的规律与Pt层厚度和周期数具有强烈的依赖关系。在[Co(4 Å)/Pt(6 Å)]n(2≤n≤22)多层膜中，反常霍尔电阻率(ρAH)、电阻率(ρxx)、拟合参数a’和b随周期数n呈现周期性振荡，这与Co/Pt界面散射紧密相关；这四者之间的相位关系并不是同相位和反相位。在Co(4 Å)/Pt(tPt Å)/Co(4 Å)多层膜中，ρAH、ρxx、拟合参数a’和b随Pt隔离层厚度的增加呈现周期性振荡；ρAH、拟合参数a’和b为同相位关系，ρxx与三者反相位；在Co(4 Å)/Pt(tPt Å)/[Co(4 Å)/Pt(6 Å)]2多层膜中，ρAH、ρxx和b随Pt隔离层厚度的增加呈现振荡行为；ρAH与b同相位，然而ρxx与b反相位；这些振荡行为与Pt隔离层的极化紧密相关。实验测试结果进一步证实了样品的结构有可能影响参数之间的相位关系。采用反铁磁CoO层，在Co(5 Å)/Pt(32 Å)/Co(5 Å)/CoO(tCoO Å)/Pt(20 Å)多层膜中，顶层Co和底层Co均存在偏置的磁滞廻线，这可能由于顶层Co的界面交换偏置和两个Co层之间层间耦合的竞争作用引起的；CoO以非化学计量比的形式存在，多层膜的截止温度低于体相CoO的奈尔温度；截止温度还与CoO层的厚度紧密相关。