铁磁应变玻璃及其物理特性

Ferromagnetic strain glass and its physical properties

铁磁应变玻璃是近年来在掺杂缺陷的Ni-Mn-Ga, Fe-Pd和Fe-Ni-Cr等铁磁马氏体合金体系中发现的新玻璃现象,其本质是短程晶格应变有序和长程磁有序共存的冻结态.铁磁应变玻璃的基本结构单元是磁性纳米马氏体畴,具有转动能垒小的特点;它们在母相基体中缓慢生长、跨越很宽温区,且母相基体和纳米畴的模量随温度呈现相反的变化趋势,这些特性可导致低场驱动大磁致伸缩效应和Elinvar效应,在微型驱动传感器和精密机械中有重要应用价值.本文主要介绍了铁磁应变玻璃的宏观物理性质、微观结构特征以及功能特性;通过Ni-X-Mn-Ga(X=Co, Fe)体系的相图,阐明了铁磁应变玻璃的形成过程,以及它与马氏体相、预马氏体相的关系.此外,本文还介绍了在铁磁马氏体/铁磁应变玻璃相界区出现的奇异相变行为——铁磁应变玻璃的自发马氏体相变.基于铁磁应变玻璃的材料设计,有望为磁性材料的性能突破和功能开发带来新机遇.

Ferromagnetic strain glass is a glassy phenomenon reported in the defects of doped Ni-Mn-Ga, Fe-Pd, and Fe-Ni-Cr ferromagnetic martensitic alloy systems recently. It is essentially a frozen state with coexisting short-range lattice strain order and long-range magnetic order. The basic structural unit of the ferromagnetic strain glass is the magnetic martensitic nanodomain. The reorientation energy barrier of these nanodomains is insignificant. They grow slowly across a wide temperature region in the parent phase matrix, and the modulus of the parent phase matrix and nanodomains shows an opposite temperature-dependent tendency. These transforming properties lead to the low-field-driven large magnetostriction and Elinvar effect. Therefore, ferromagnetic strain glass alloys have potentially important applications in microactuators or sensors and precision apparatuses. This paper introduces the macroscopic physical properties,microstructural characteristics, and functional effects of ferromagnetic strain glass. Through the phase diagram of the NiX-Mn-Ga(X=Co, Fe) system, the formation of a ferromagnetic strain glass and its relationship with martensitic and premartensitic phases are clarified. Furthermore, the novel transformation behavior, i.e., the spontaneous martensitic transition of ferromagnetic strain glass in the phase boundary region between ferromagnetic martensite and ferromagnetic strain glass, is also introduced. The material design based on ferromagnetic strain glass is expected to bring new opportunities for the performance breakthrough and functionality development of magnetic materials.