Stress modulated antiferromagnetism in thin film heterostructures

在开发新的高密度逻辑和存储器器件的挑战中，由于非常低能耗器件的潜力，采用电子自旋输运作为数据矢量（即自旋电子学）的概念受到极大关注。反铁磁材料通过在铁磁体和反铁磁体界面处的磁交换偏置现象在自旋电子学器件中发挥关键作用。这种现象允许这种异质结构充当自旋阀，以根据电子的自旋来控制电子的传导。本计画研究BiFeO_3-PbTiO_3固溶体中的反铁磁性开关，其电性与磁化强度通过晶格应变耦合，表现出铁电性与反铁磁性。耦合似乎是最敏感的结构之间的相变四面体和菱面体对称性。实验方案将集中在脉冲激光沉积和表征薄膜的BiFeO 3-PbTiO 3组合物，在各种基板上，导致电场和机械应力如何相互作用，以调制反铁磁序参数的理解。

In the challenge to develop new, high- density logic and memory devices, the concept of employing electron spin transport as the data vector (i.e. spintronics) is of great interest due to the potential for very low energy consumption devices. Antiferromagnetic materials can play a pivotal role in spintronic devices through the phenomenon of magnetic exchange bias at the interface between a ferromagnet and an antiferromagnet. This phenomenon allows such heterostructures to act as spin-valves to control the conduction of electrons according to their spin. The ability to modulate the exchange bias, for example by switching the antiferromagnetism on and off, would be a valuable concept in spintronic device design.This project investigates such antiferromagnetic switching in BiFeO3-PbTiO3 solid solutions, exhibiting both ferroelectricity and antiferromagnetism, in which the electrical polarization and the magnetization are coupled via the lattice strain. The coupling appears to be most sensitive at a structural phase transition between tetragonal and rhombohedral symmetries. The experimental programme will focus on the pulsed laser deposition and characterization of thin films of BiFeO3-PbTiO3 compositions, on a variety of substrates, leading to an understanding of how electric field and mechanical stress can interact to modulate the antiferromagnetic order parameter.