A significant progress in the development of thin-film multiferroic devices has been achieved by Prof. Xiaoguang Li’s group in the Physics Department of University of Science and Technology of China, through collaboration research with Prof. Cewen Nan in Tsinghua University as well as Prof. Longqing Chen in Pennsylvania State University. The work has been published on Advanced Materials (DOI: 10.1002/adma.201402774) with the title of “Non-volatile 180º Magnetization Reversal by an Electric Field in Multiferroic Heterostructures”. Mr. Shengwei Yang, a doctor student in USTC, is the first author of the article.

 
Non-volatile 180º magnetization reversal by an electric field in multiferroic
heterostructures published on Advanced Materials 

It is known that the traditional magnetic random access memories are usually driven by magnetic fields, thus the memory cell presents a relatively larger volume and energy loss. Considering the urgent need for device miniaturization and multi-functionalization as well as low energy consumption, the development of new materials with two or even more functional features for designing multi-functional devices has attracted much attentions in recent years. Since the multiferroic materials have ferroelectric, ferromagnetic and unique magnetoelectric properties, it is possible to rotate magnetization and manipulate spin states via electric fields, finally leading to the breakthrough in spintronics with advantage in miniaturization and multi-functionalization. However, the magnetoelectric coupling effect in single phase multiferroic materials is weak and only exists at low temperature, which is not favorable for practical applications. Fortunately, in the multiferroic heterostructures, one can manipulate magnetization rotation by electric control at room temperature.

Usually, the electric manipulation to magnetism shows a volatile effect which cannot be used for information storage, because that the magnetic variation vanishes after the electric field removal. Even for the nonvolatile electric driven magnetization rotation, the observed reversible non-volatile rotation is distributed irregularly, appears in only very limited areas with complex operations. Thus a way to achieve a reversible non-volatile magnetization rotation over a large area of heterostructure by a convenient method, and to make the rotation macroscopically measurable and practical, is still one of the challenges in the field of multiferroic applications.

To address these questions, a new and promising side polarization configuration is designed to effectively rule out the impact of the ferroelectric field effect, and provide a significant piezostrain for the magnetization rotation. Via electric polarization control, the magnetoelastic anisotropy induced by the strain transferred from polarized PMN-PT competes with the interface magnetic anisotropy. As result, even without applying external magnetic fields, the electric driven 90º and even 180º nonvolatile magnetization rotations are achieved at room temperature. Based on this effect, an electric controlled tri-state spin valve prototype device as well as a digital single-pole double-throw switch and a three-state output gate logical devices are designed. 

This work was supported by National Natural Science Foundation of China and 973 Program.

 

Linking to the paper:
http://onlinelibrary.wiley.com/doi/10.1002/adma.201402774/full

(YANG Shengwei,School of Physical Sciences)