多阶有序钙钛矿多铁性材料的高压制备与物性

钙钛矿是研究磁电多铁性最重要的材料体系之一.由于高的结构对称性,在以往的立方钙钛矿晶格中尚未发现多铁现象.另外,现有的单相多铁性材料很难兼容大电极化和强磁电耦合,严重制约多铁性材料的潜在应用.本文简单综述了利用高压高温条件制备的两个多阶有序钙钛矿氧化物的磁电多铁性质.在具有立方晶格的多阶钙钛矿LaMn_3Cr_4O_(12)中,观察到自旋诱导的铁电极化,表明该材料是第一个被发现的具有多铁性的立方钙钛矿体系.在另一个多阶有序钙钛矿BiMn_3Cr_4O_(12)中,随温度降低该材料依次经历了I类多铁相和II类多铁相.正因为这两类不同多铁相的同时出现,BiMn_3Cr_4O_(12)同时展示了大的电极化强度和强的磁电耦合效应,并且通过不同的电场调控可实现四重铁电极化态,为开发多功能自旋电子学器件与多态存储提供了先进的材料基础.

High pressure synthesis and physical properties of multiferroic materials with multiply-ordered perovskite structure

Perovskite is one of the most important material systems for magnetoelectric multiferroic study. However, multiferroic is not expected to occur in a cubic perovskite on account of the highly symmetric crystal structure. Besides, magnetoelectric multiferroics with large ferroelectric polarization and strong magnetoelectric coupling have not been found to occur simultaneously in a single-phase multiferroic material discovered so far, challenging to the potential applications of this kind of material. Here we briefly review two multiferroic materials with multiply-ordered perovskite structure synthesized under high pressure and high temperature conditions. In the cubic perovskite LaMn₃Cr₄O₁₂, we observed spin-induced ferroelectric polarization, providing the first example where ferroelectric takes place in a cubic perovskite material. In another multiply-ordered provskite BiMn₃Cr₄O₁₂, type-I and type-Ⅱ multiferroic phases successively developed when cooled. It provides a rare example where two different types of multiferroic phases occur subsequently so that both large polarization and strong magnetoelectric effect are achieved in a single-phase material. In addition, since double ferroelectric phases take place in BiMn₃Cr₄O₁₂, one can obtain four different polarization states by adopting different poling procedures, thus opening up a new way for generating multifunctional spintronics and multistate storage devices.