一级磁相变合金薄膜/铁电衬底异质结构中的电控磁效应研究

The electrical-controlled magnetism has attracted more and more attention due to its promising applications in multifunctional devices、information storage and low-consuming devices. Magnetoelectric composites have been the focus of this field since they can show large magnetoelectric effect at room temperature. As we know, the phase transition in first-order magnetic-phase-transition alloy can be driven by stress and large change of magnetization can be observed around the phase transition, which make it as an important element of magnetoelectric composites. In this project, we deposit the films of FeRh and NiMn-based ferromagnetic shape memory alloys on BaTiO3 or Pb(Mg1/3Nb2/3)O3–PbTiO3 substrates and investigate the effect of electrical-controlled magnetism on these heterostructures. Usually, the study of magnetoelectric effect only focuses on the change of magnetization, which is far from enough to fully utilize the magnetic effects in magnetic-phase-transition alloys. In this project, we will study the electrical control of magnetocaloric, magnetoresistance, Hall effect, magnetic optical kerr effect and exchange bias effect in magnetic-phase-transition alloy films through converse piezoelectric and ferroelectric field effects. This research will provide the experimental basis for extending the application fields of magnetic-phase-transition alloy and the effect of electrical controlled magnetism.

电控磁效应因在多功能器件、信息存储和低功耗元件中的重要应用前景而备受关注。复相磁电材料因在室温时具有大的电控磁效应而成为该领域的研究重点。众所周知，一级磁相变合金的相变能被应力所驱动且在相变点伴随着磁化强度的突变，所以成为了复相磁电材料中的重要组成单元。本项目中，我们通过在BaTiO3或Pb(Mg1/3Nb2/3)O3–PbTiO3衬底上生长FeRh和NiMn基铁磁形状记忆合金薄膜，构造复相磁电异质结构并从中开展电控磁效应研究。通常的电控磁效应主要研究电场对磁化强度大小的调控，而这样的研究没有充分利用一级磁相变合金丰富的磁效应。在本项目中，我们将利用铁电衬底的逆压电效应和铁电场效应开展电场对合金薄膜的磁制冷、磁电阻、霍尔效应、磁光克尔效应以及交换偏置等效应的研究，为拓宽磁相变合金材料的应用范围和将电控磁效应研究推向更广阔领域提供实验基础。

电控磁效应的研究对发展多功能低功耗磁性器件具有重要意义。一级磁相变材料的磁性易受外场调控，是理想的电控磁研究对象。我们在一级磁相变体系内开展了电控磁效应研究，其主要成果包括：（1）在Fe(Rh,Pd)磁相变合金薄膜与压电陶瓷PMN-PT组成的异质结构中，在室温条件下获得了大的电控磁效应。（2）在FePt薄膜与PMN-PT组成的异质结构中，利用电场产生的应变对剩磁的调控，实现了电场调控的多态存储。（3）在LaFeSiH薄带和PMN-PT组成的异质结构中实现了电场对相变温度和磁制冷效应的调控。（4）在NiMnCoSn薄带和（011）取向的PMN-PT组成的异质结构中，实现了电场对磁性和磁制冷性质的非易失调控。（5）在钙钛矿锰氧化物相变薄膜中，通过电场控制氧离子的迁移实现了对磁性的调控。这些研究成果对优化磁相变材料的性能具有重要意义。