基于稀释反铁磁增强交换偏置效应调控软磁金属薄膜微波磁性的研究

Exchange bias effect has been employed to increase the effective magnetic anisotropy and ferromagnetic resonance frequency of soft magnetic metallic thin films. However, the present related studies are focused on the thickness effect of ferromagnetic layers, and overlook the influences on coercivity and damping. In this proposal, we propose that the microwave characteristics of soft magnetic metallic thin films should be effectively tuned by the enhanced exchange bias effect with diluted antiferromagnets. Firstly, aimed at the microwave applications of soft magnetic thin films, we will investigate and obtain the rules by which the dilution of antiferromagnets affects the exchange bias, and realize the enhancement of exchange bias at room temperature. We will also design and deposit exchange-bias bilayers as a model system, with precisely controlled interfaces and dilutions with nonmagnetic elements, to further study and clarify the influence mechanisms by diluted antiferromagnets. Secondly, the dependences of coercivity on the dilution of antiferromagnets and exchange bias will be studied, and their correlation will be emphasized. The different origins between the increase of coercivity and exchange bias will be revealed. Thirdly, by microwave characterizations and the fitting analysis based on magnetization dynamics, we will differentiate the magnetic anisotropies, and investigate the dependences and origins of microwave damping. On the basis of these studies, we will realize a remarkable increase of microwave resonance frequency of soft magnetic thin films by enhanced exchange bias effect with diluted antiferromagnetic layers, and effective controls of coercivity and damping. The results of this project are valuable for the understanding of exchange bias effect, and significant for the future applications of soft magnetic metallic thin films among microwave IC devices.

交换偏置效应可有效提高软磁金属薄膜的有效磁各向异性场及铁磁共振频率，而现有研究中其调变手段局限于铁磁层厚度调制，且忽视了对矫顽力和阻尼的影响。对此，本项目提出基于稀释反铁磁增强交换偏置效应调控软磁金属薄膜的微波磁性。首先，将针对软磁薄膜的微波应用，研究稀释反铁磁对交换偏置的影响规律，实现室温下交换偏置的增强，同时基于交换偏置模型体系，精确控制界面、非磁掺杂等因素，探讨反铁磁稀释效应的影响机制；其次，将研究矫顽力随反铁磁稀释和交换偏置的变化规律，总结三者之关联，揭示矫顽力升高与交换偏置机制的差异；再次，通过微波表征及磁化动力学拟合分析，揭示磁各向异性，探讨阻尼因子的变化规律及来源机制。在此基础上，通过稀释反铁磁增强交换偏置效应实现软磁薄膜微波共振频率的大幅提升，以及对矫顽力和阻尼的抑制调控。本项目研究成果对于交换偏置机制的进一步揭示以及软磁金属薄膜在微波集成器件领域的推广应用具有重要意义。

本项目针对微波集成器件发展需求，利用包括反铁磁稀释增强交换偏置等手段，来实现软磁金属薄膜微波磁性的有效调控，包括共振频率的提升、矫顽力及阻尼的有效调控，并深入研究其中涉及的物理机制。本项目在包括FeNi/IrMn等多个铁磁/反铁磁体系中实现了交换偏置效应，并利用MgO稀释IrMn，实现了交换偏置效应的增强，并讨论了交换偏置体系中，偏置场、矫顽力、阻尼等之间的相互影响和规律。通过倾斜溅射，实现了Co2FeSi以及FeCo基薄膜磁各向异性的大幅提升，实现了超高磁各向异性场。通过引入稀土元素增强自旋轨道耦合效应，以及通过利用自旋泵浦效应，实现了阻尼的增强。通过微磁学模拟，对偏心Co环等多个纳米结构体系中的磁化过程进行了模拟，讨论了结构参数对于形成稳定磁化状态的影响。设计了四方Mn3Ge基合金结构中磁补偿状态，验证了其中存在的交换偏置效应，并设计开发了包括自旋零能隙半导体、磁结构相变合金在内的多个新材料体系。总之，本项目较为系统地开展了磁各向异性、磁化动力学阻尼效应和机制等方面的研究，通过反铁磁稀释在实验上实现了交换偏置效应的增强，以及共振频率的提高，完成了预期的研究目标。