钙钛矿稀土铬(锰)氧化物中的零场冷交换偏置效应与斯格明子研究

Study on magnetic phenomena and magnetoelectric coupling in perovskite type rare earth transition metal oxides is one of the frontiers in condensed matter research and magnetic storage. At present, study on exchange bias effect after zero field cooled process has just started, and a systematic study is necessary to answer questions including the details of the metastable spin structure, and the mechanism of the generation of the structure etc. In this project, we are going to use RCrO3, where we found exchange bias effect after zero field cooled process, as a platform for the study of exchange bias effect after zero field cooled process. Samples with different crystallization and morphology will be used, and multi characterization and measuring techniques including magnetic measuring, scanning electron microscopy, energy dispersive X-Ray spectroscopy and powder neutron diffraction will be used to give a systematic characterization and study of exchange bias effect after zero field cooled process. Measuring of anisotropic resistivity, magnetization, electric polarization and second-harmonic (SH) etc. will be used to study spin orderings including magnetic skyrmions and magnetoelectric coupling in La2-2xSr1+2xMn2O7. The simultaneous study of the zero field cooled exchange bias effect in RCrO3 and skyrmions in la2-2xSr1+2xMn2O7 may bring a better understanding of the details of the spin structure which play a key role in the generation of zero field cooled exchange bias. Original and fruitful results are expected.

钙钛矿过渡金属稀土氧化物中的磁现象和磁电耦合是凝聚态物理和磁存储领域的研究前沿。目前，零场冷交换偏置现象的研究尚处于起始阶段，许多重要问题的解明，如其中亚稳态磁结构的结构细节，产生机制等尚有待系统性的研究。本项目拟利用我们已经发现的具有零场冷交换偏置效应的稀土铬氧化物材料平台，采用不同结晶情况和形貌的样品，结合多种表征手段和低温强磁场等极端条件下的多种测量技术（包括磁测量，扫描电镜,EDX,中子散射等），深入系统地研究RCrO3中的零场冷交换偏置现象; 通过光学二次谐波及多种物性测量手段来研究La2-2xSr1+2xMn2O7单晶中的skyrmions等手征自旋序及磁电耦合。两个体系的同步研究有助于在斯格明子等手征磁体的研究数据基础上，给RCrO3中造成零场冷交换偏置的亚稳态磁结构的研究带来启发，揭示其亚稳态磁结构的结构细节及产生机制，以期做出原创性的成果。

过渡金属氧化物的物性及应用是凝聚态物理与化学领域的主要研究内容之一。表面界面引起的磁现象不仅催生了目前广泛应用的磁存储设备，而且是目前凝聚态物理的研究前沿。我们以RCrO3体系中的零场冷交换偏置效应为主线，进行了包括Y1-xPrxCrO3，Eu0.9Pr0.1CrO3多晶样品，Y0.9Pr0.1CrO3纳米样品，YCrO3/ PrCrO3复合样品的制备及结构，成分分析和磁性测量工作，分别在多晶块材Y1-xPrxCrO3， Eu0.9Pr0.1CrO3，颗粒较大的Y0.9Pr0.1CrO3纳米颗粒样品，及充分融合的YCrO3/ PrCrO3样品中发现了负向的零场冷交换偏置现象，并在高温烧结的Y0.9Pr0.1CrO3纳米多晶样品中发现了正向的零场冷交换偏置现象。通过对上述不同体系中发现的零场冷和场冷交换偏置现象的比较分析，解明了该RCrO3体系中零场冷交换偏置的产生机制，找到了零场冷交换偏置和成分，温度，结构的关系，发现了在一定范围内连续调控零场冷交换偏置大小的方法。零场冷交换偏置的产生主要由磁格子间的耦合主导，具体耦合情况和各磁畴结构及其分布，磁格子的磁矩取向，磁格子间的耦合强度决定，其形成过程受温度和外加磁场的影响。此外，我们还进行了La2-2xSr1+2xMn2O7单晶的生长、结构表征和磁，光测量，以及铜氧化物复合材料制备和在传感器方面的应用研究。