新型Fe3Se4基各向异性纳米结构的硬磁性能调控和矫顽力机制

This project will study new type Fe3Se4-based hard magnetic nanostructures without rare earth elements and noble metal Pt. The magnetic Fe3Se4 compound has the characteristic that its magnetocrystalline anisotropy constant is to be 1.0x107 erg/cm3. It is rare for materials without rare earth or noble metal elements to possess such high anisotropy. First-principles calculations will be used to predict the effects of substitution of different Fe atomic lattices by other transition metal, M, on the magnetic performance of Fe3-xMxSe4 compounds because of changing the magnetic ionic exchange interactions. The results from first-principles calculations will be used to direct our experimental researches. Suitable substitution of iron atoms in Fe3Se4 by other transition metal atoms, M, will be performed to increase the saturation magnetization and Curie temperature of Fe3-xMxSe4 hard magnets. We will systematically study the growth regularity and optimal growing conditions of Fe3-xMxSe4 nanostructures, including anisotropic nanocrystals, one dimensional nanowires ordered lattices and grain oriented anisotropic films with uniform phase composition and controlled microstructure. The correlation between the hard magnetic properties and phase composition, doped elements of the nanostructures and size effect will be studied in detailed. The hard magnetic properties, such as coercivity and rectangle degree of hysterysis loops, will be enhanced through tuning the microstructure and doped atoms of Fe3-xMxSe4 nanostructures. Reversal magnetization mechanisms of different Fe3-xMxSe4 nanostructure system will be demonstrated clearly. The coercivity temperature-dependence of anisotropic Fe3-xMxSe4 hard magnetic nanostructures will be studied. In further, Fe3-xMxSe4 hard magnetic nanostructures will be exploited as a high cost performance and high density perpendicular magnetic recording medium, because the high anisotropy of Fe3-xMxSe4 compounds is helpful to increase the thermal stability of storage units and storage density. The present proposal will not only exploit new type high magnetocrystalline anisotropic hard magnetic nanomaterials, but also supply more experimental data and theoretical guide for a candidate for hard magnetic material applications, such as in recording media.

本项目研究一种不含稀土和贵金属Pt的新型Fe3Se4基硬磁纳米材料体系。运用第一性原理计算指引实验研究，寻找合适的金属M原子替代具有高磁晶各向异性常数的Fe3Se4合金中的Fe原子，调控Fe3-xMxSe4化合物中金属离子间的交换耦合作用，提高化合物的饱和磁化强度和居里温度等磁性质。可控制备出新型Fe3-xMxSe4硬磁相各向异性纳米晶颗粒、一维纳米线有序阵列和各向异性生长的纳米薄膜，掌握不同纳米结构的形成规律和最佳制备条件。阐明不同维度、形貌的纳米结构的元素组成、成分配比、生长条件等因素对磁性纳米结构的硬磁性质的影响；纳米结构的尺寸效应、微观结构与其矫顽力、磁滞回线矩形度之间的关系及它们的反磁化机制。阐明各向异性Fe3-xMxSe4硬磁相纳米结构的矫顽力机制及其温度依赖特性，为Fe3-xMxSe4硬磁相纳米结构在新型高密度垂直磁记录介质上的应用提供实验依据和理论支持。

在国家自然科学基金委面上项目：新型Fe3Se4基各向异性纳米结构的硬磁性能调控和矫顽力机制（批准号：51371175，执行时间：2014年1月-2017 年12月）的资助下，项目负责人及其研究团队期间共发表综述性论文1篇、学术论文9篇、提交中国发明专利3项；其中Chemistry of Materials 1篇、Nanoscale 1篇、欧洲物理(EPL) 1篇、2D Materials 1篇、美国应用物理杂志(Journal of Applied Physics) 2篇、RSC Advances 2篇以及Materials Research Bulletin 1篇。项目按计划书内容有序开展，在成功地通过第一性原理计算研究了各向异性Fe3-xCrxSe4晶体的生长机制和磁晶各向异性的基础上，以熔盐法制备出Fe3-xCrxSe4单晶，以溶液化学法制备了各向异性Fe3-xCrxSe4纳米结构材料。研究了结构演化、元素组成和纳米尺寸效应对Fe3Se4纳米线阵列、Fe3-xCrxSe4纳米结构的磁性能产生的影响。发现内应力增加和纳米尺寸效应导致Fe3-xCrxSe4纳米结构的居里温度，比块体提高约100 K，达到420 K。发现Fe2.5Cr0.5Se4单晶的室温磁晶各向异性常数为1.2 Merg/cm3，比Fe3Se4高一个数量级，在不含稀土和贵金属Pt的铁基化合物中没有报道过。由于优异的单轴磁晶各向异性，Fe2.3Cr0.7Se4纳米结构的室温矫顽力达到12 kOe。本项目研究表明，调控磁性离子间的相互作用是提高以Fe3Se4为基的铁基化合物硬磁性能的有效途径。在研究铁硒基无稀土硬磁材料的基础上，解决了一步化学液相法制备具有窄相区特征的铁基β-FeSe超导体纳米片中遇到的化学问题。重点研究了β-FeSe超导纳米片与化学成分相关的反铁磁序-超导序-反铁磁序转变等物理问题和制备β-FeSe超导纳米器件的材料问题。