锰氧化物在顺磁区的电子顺磁共振线宽增宽的物理机制研究

The electron paramagnetic resonance (EPR) study of colossal magnetoresistance (CMR) manganites have attacted much attention in the field of condensed matter physics. However, a considerable amount of controversy exists concerning the EPR linewidth broadening mechnism in the high temperature paramagnetic region. The applicant in the previous work found that the spin-spin exchange-narrowed interaction and the small polaron contributed to the EPR linewidth of La0.9Te0.1MnO3 above the Curie-Weiss temperature. A salient question to ask is the following: is this model applicable to the other manganites? The magnetic resonance equipment in the high magnetic filed, Chinease Academy of Sciences provides a good platform and opportunity for the applicants to carry out the related work. This proposal aiming at the cultivating projects-steady state high magnetic-field magnetic resonance technology, intends to study the EPR spectra of hole-doped and electron-doped manganites. The applicants will study the effects of different single-electron bandwidth and band filling ratio on the EPR linewidth parameters and establish a universal model that can describe the EPR line width behavior above the Cure-Weiss temperature in order to clarify the EPR linewidth broadening mechanism of the CMR materials. The proposal is expected to lay the foundation for deeper understanding and study of the physical mechnism of the CMR effect and the behavior of high-temperatures spin dynamics.

近年来在凝聚态物理领域备受关注的庞磁电阻锰氧化物的电子顺磁共振（EPR）谱得到了广泛的研究，然而关于高温顺磁区的EPR线宽增宽的物理机制还存在着很大的争议。申请者在前期工作中发现La0.9Te0.1MnO3的EPR线宽在居里-外斯温度以上是由自旋-自旋交换变窄的相互作用和小极化子所贡献的。那么对于其他锰氧化物体系，这个模型是否适用呢？依托合肥物质科学研究院而建立的稳态强磁场磁共振技术为申请者开展相关工作提供了很好的平台和契机。本申请针对培育项目下的稳态强磁场磁共振技术，拟选取空穴型和电子型掺杂锰氧化物单晶为研究对象，通过研究不同掺杂类型及不同的单电子带宽和能带填充比例对EPR线宽参数的影响规律，建立一个能够描述EPR线宽行为在居里-外斯温度以上的普适性的模型，澄清CMR材料体系中EPR信号线宽的增宽效应的物理机制的争议，为深入理解和研究CMR效应的物理机制和高温自旋动力学行为奠定基础。

近年来在凝聚态物理领域备受关注的庞磁电阻锰氧化物的电子顺磁共振（EPR）谱得到了广泛的研究，然而关于高温顺磁区的EPR 线宽增宽的物理机制还存在着很大的争议。那么对于具有顺磁-铁磁相变的钙钛矿结构锰氧化物来说，在高温顺磁区是否存在一个普适性的模型能很好的描述EPR线宽行为呢？本项目制备了电子型和空穴型掺杂锰氧化物样品，其中电子型掺杂锰氧化物La1-xTexMnO3的EPR研究结果表明，其EPR谱的线宽可以由自旋-自旋交换变窄的相互作用和极化子贡献这个模型很好地描述，这个模型的普适性需要空穴型掺杂锰氧化物单晶样品的EPR谱来进一步验证，从而为深入理解和研究CMR 效应的物理机制和高温自旋动力学行为奠定基础。