变磁性FeRh合金/铁磁金属双层膜的界面交换耦合及其调控研究

FeRh alloy possesses a particular antiferromagnetic to ferromagnetic phase transition. Consequently, a bilayer composed of both FeRh alloy and ferromagnetic metal film displays the exchange bias and exchange spring effects before and after the magnetic transition of FeRh, respectively. Therefore, FeRh alloy can be potentially applied in the thermally assisted magnetic recording media, the spintronic devices, etc. However, FeRh/ferromagnetic metal bilayers display various interesting physical behaviors, such as the exchange bias effect, the fourfold magnetic anisotropy behaviors, which are different from the previous observations in the usually studied systems with exchange coupling. Unfortunately, these special behaviors observed in FeRh/ferromagnetic metal bilayers cannot been fully understood by means of the existing theory and model about the interfacial exchange coupling. Based on our research experiences and achievements on both the exchange bias effect and the FeRh alloy, in this project, we will carry out an investigation on the interfacial exchange coupling and its control in FeRh/ferromagnetic metal bilayers. By means of controlling the magnetic structure of FeRh surface with the growth parameters, we will study the effect of the FeRh interfacial magnetic structure on the exchange bias effect of FeRh/ferromagnetic metal bilayers. By means of constructing FeRh/amorphous ferromagnetic metal bilayers, we will understand the intrinsic relationship between the interfacial exchange coupling and the fourfold magnetic anisotropy behaviors observed in amorphous ferromagnetic alloys. By means of the study on the electric control of the interfacial exchange coupling in FeRh/ferromagnetic metal bilayers, we are able to develop a low energy consumption technology of electrically assisted magnetic recording. Our research in this project may provide technical storage and theoretical understanding for the application of FeRh/ferromagnetic metal bilayers.

FeRh合金具有独特的反铁磁-铁磁相变，与铁磁薄膜构成的双层膜在相变前后表现出交换偏置与交换弹簧两种效应，从而在热辅助磁存储、自旋电子学器件中有着广泛的潜在应用。然而，FeRh/铁磁金属双层膜表现出与传统交换耦合体系不同的物理性质，例如交换偏置效应、四重对称磁各向异性等，利用现有的界面交换耦合理论与模型尚不能完全理解。基于我们在交换偏置效应、FeRh薄膜的研究与积累基础上，本项目拟针对FeRh/铁磁金属双层膜的界面交换耦合及其调控开展研究，通过生长控制FeRh表面磁结构，探索界面反铁磁结构对FeRh/铁磁金属双层膜界面交换偏置效应的影响规律；构建FeRh/非晶铁磁合金双层膜，理解界面交换耦合与非晶铁磁合金中四重对称磁各向异性行为的关联规律；研究电场控制FeRh/铁磁金属双层膜界面交换耦合效应的物理规律，探索低功耗的电场辅助磁存储技术原理，为FeRh/铁磁双层膜的应用提供技术储备与理论基础。

FeRh合金具有独特的反铁磁-铁磁相变，与铁磁薄膜构成的双层膜在相变前后表现出交换偏置与交换弹簧两种效应，从而在热辅助磁存储、自旋电子学器件中有着广泛的潜在应用。本项目中，我们在外延FeRh/非晶CoFeB异质结中，实现了非晶材料对外延铁磁、反铁磁薄膜磁晶各向异性的取向与强度的映射效应，薄膜的有效磁阻尼和双磁子散射随着FeRh由反铁磁转变为铁磁态而增大。研究了界面交换耦合对铁磁薄膜磁化翻转的影响，CoFe/FeRh异质结中，由于与FeRh层的界面交换耦合作用，CoFe表现面内四重磁各向异性，磁化机制转变为畴壁形核与位移。使用铁磁共振测试定量研究了FeRh薄膜的磁晶各向异性，铁磁态时，[100]为易磁化方向；反铁磁态时，改变为难磁化方向，磁晶各向异性提高约4倍。利用MgO缓冲层，在PMN-PT铁电衬底上外延生长了FeRh薄膜，实现了电场对多态磁化翻转的调控。在[Ni/Co]3/Rh异质结中，实现了自旋轨道矩电流驱动磁化翻转，自旋轨道矩效率随着Rh厚度增加而增大，Rh/Co异质结界面DMI常数随着Rh厚度增加而增大。研究了基于相变材料FeRh的垂直磁化异质结的电流诱导磁化翻转行为，自旋轨道矩效率表现出与FeRh磁性相变一致的温度滞后行为，当FeRh处于反铁磁态较之其处于铁磁态自旋轨道矩效率提高了约450%，在FeRh反铁磁和铁磁态时都实现了电流诱导的无外场辅助的垂直磁化翻转。研究了具有褶皱形貌CoFeB薄膜高频磁性及应变调控研究，表现出优异的应变调谐高频性能的特性。我们的研究可以为FeRh应用在未来热辅助磁存储、自旋电子学器件提供技术储备与理论基础。在项目资助下，我们以通讯作者发表SCI论文17篇，申请专利1项。