双钙钛矿Sr2FeMoO6中低场磁阻的研究

Due to its higher Curie temperature (Tc~415K) and considerable high low-field magnetoresistance at room-temperature, magnetic double pervoskite Sr2FeMoO6 material has been become one of the most promising materials for the application. Fe/Mo anti-site defects and grain boundary strength effects significantly influence the low-field magnetoresistance response, and the two factors can be tuned by the preparation technique and strategy well. How to effectively improve the low-field magnetoresistance is the key point of the practice application. In this project, we select the Sr2FeMoO6 as research object to conduct the low-field maegnetoresistance investigation, including: (1) regulation and characterization of Fe/MO anti-site defect; (2) comparative studies of the effects of the Fe/Mo anti-site defects and grain boundary strength on the low-field magnetoresistance; (3) at room temperature, optimizing the low-field magnetoresistance by a facile and effective method. By the investigation in the project, it is tend to master the experimental strategy of controlling the anti-site defect content effectively and quantitatively, and improve the characterization technology. The laws of the anti-site defect and grain boundary impact on the final trend of low-field magnetoresistance can be revealed. At last, we propose a facile and effective post-treatment strategy to optimize the low-field magnetoresistance without sacrificing other physical properties, such as magnetization and the Curie temperature. By doing so, it is proposed to provide theoretical guidance and technologies for the application in spintronis devices and other practical applications.

双钙钛矿磁性氧化物Sr2FeMoO6, 具有较高的居里温度（~415K）和优越的室温低场磁阻效应, 成为最有应用前景的材料之一。Fe/Mo反位缺陷和晶界强度显著影响低场磁阻效应，二者可通过制备工艺调控。如何有效提高低场磁阻效应是Sr2FeMoO6走向实际应用的关键所在。本项目基于Sr2FeMoO6材料展开低场磁阻行为的研究，包括：（1）Fe/Mo反位缺陷的调控和表征；（2）比较研究Fe/Mo反位缺陷和晶界强度对低场磁阻效应的影响；（3）常温下，通过有机小分子修饰晶界，简单有效优化低场磁阻。希望通过本项目的研究，掌握有效控制Fe/Mo反位缺陷的制备工艺，完善其表征技术。揭示Fe/Mo反位缺陷和晶界对低场磁阻总趋势的影响规律。在保证其它物理性能（居里温度和磁性）基本不变的情况下，提出一种简单有效的优化低场磁阻效应的常温制备工艺，为该材料能够在自旋电子气等实际应用提供理论指导和技术路线。

在本项目的资助下，发表第一作者SCI论文共计9篇；培养在读研究生两名；成功培养一名本科生到中科院物理所攻读硕博学位；签约一项横向项目（到账21万）。.具体内容包括：利用固相烧结方法，以双钙钛矿Sr2FeMoO6作为研究对象，重点研究了Fe/Mo反位缺陷调控和晶界修饰及其对磁阻的影响，初步探索了游离态电子态密度和Fe/Mo反位缺陷对Sr2FeMoO6物理性能的影响，开展如下工作：（1）本项目创新性地在Sr2FeMoO6晶界处引入铁磁性绝缘材料，在保证居里温度和磁性能不变的情况下，实现了低温低场磁阻增加一倍。（2）在Sr2Fe(1+x)MoO6复合物体系中，位于晶界处的磁性Fe元素含量显著影响Fe/Mo反位缺陷和晶界强度，进而影响Sr2FeMoO6磁阻以及其他物理性能；研究了非磁性金属元素B位部分取代对Sr2FeMoO6结构以及物性的影响。（3）通过调控烧结温度和降温速率，能够有效控制Fe/Mo反位缺陷含量以及晶界状况，从而定性控制磁性性能和磁阻行为；A/B位元素部分替代导致的带填充效应，有效调控费米能级附近载流子密度以及电子的自旋极化率，进而控制铁磁耦合强度（Tc）以及磁阻行为。（4）研究了化学价态平衡-相-制备工艺之间的关联，初步探索了制备难度较大的纯相双钙钛矿的优化方案。总体上，本项目圆满完成了预期目标。