Voltage control of magnetism (VCM) is attracting increasing interest and exciting significant research activity driven by its profound physics and enormous potential for application. This review article aims to provide a comprehensive review of recent progress in VCM in different thin films. We first present a brief summary of the modulation of magnetism by electric fields and describe its discovery, development, classification, mechanism, and potential applications. In the second part, we focus on the classification of VCM from the viewpoint of materials, where both the magnetic medium and dielectric gating materials, and their influences on magnetic modulation efficiency are systematically described. In the third part, the nature of VCM is discussed in detail, including the conventional mechanisms of charge, strain, and exchange coupling at the interfaces of heterostructures, as well as the emergent models of orbital reconstruction and electrochemical effect. The fourth part mainly illustrates the typical performance characteristics of VCM, and discusses, in particular, * Corresponding author. Tel: +86-10-62781275; fax: +86-10-62771160 E-mail address: songcheng@mail.tsinghua.edu.cn † Present at Max-Planck Institute of Microstructure Physics, Weinberg 2, D-06120Halle, Germany 2 its promising application for reducing power consumption and realizing high-density memory in several device configurations. The present review concludes with a discussion of the challenges and future prospects of VCM, which will inspire more in-depth research and advance the practical applications of this field.

We investigated the dependence of T C and magnetoresistance (MR) on gate voltages ( V G ) in the 20-nm-thick high-quality La 0.6 Sr 0.4 MnO 3 (LSMO) Hall bar gated by ionic liquid (more Reversible Ferromagnetic Phase Transition in ElectrodeGated ManganitesBin Cui , Cheng Song , * Guangyue Wang , Yinuo Yan , Jingjing Peng , Jinghui Miao , Haijun Mao , Fan Li , Chao Chen , Fei Zeng , and Feng Pan * The electronic phase transition has been considered as a dominant factor in the phenomena of colossal magnetoresistance, metal-insulator transition, and exchange bias in correlated electron systems. However, the effective manipulation of the electronic phase transition has remained a challenging issue. Here, the reversible control of ferromagnetic phase transition in manganite fi lms through ionic liquid gating is reported. Under different gate voltages, the formation and annihilation of an insulating and magnetically hard phase in the magnetically soft matrix, which randomly nucleates and grows across the fi lm instead of initiating at the surface and spreading to the bottom, is directly observed. This discovery provides a conceptually novel vision for the electric-fi eld tuning of phase transition in correlated oxides. In addition to its fundamental signifi cance, the realization of a reversible metalinsulator transition in colossal magnetoresistance materials will also further the development of four-state memories, which can be manipulated by a combination of electrode gating and the application of a magnetic fi eld.

Electrical manipulation of lattice, charge, and spin has been realized respectively by the piezoelectric effect, field-effect transistor, and electric field control of ferromagnetism, bringing about dramatic promotions both in fundamental research and industrial production.

We investigate the exchange coupling between perpendicular anisotropy (PMA) Co/Pt and IrMn in-plane antiferromagnets (AFMs), as well as tunneling anisotropic magnetoresistance (TAMR) in [Pt/Co]/IrMn/AlO_{x}/Pt tunnel junctions, where Co/Pt magnetization drives rotation of AFM moments with the formation of exchange-spring twisting. When coupled with a PMA ferromagnet, the AFM moments partially rotate with out-of-plane magnetic fields, in contrast with being pinned along the easy direction of IrMn for in-plane fields. Because of the superior thermal tolerance of perpendicular exchange coupling and the stability of moments in ~6 nm-thick IrMn, TAMR gets significantly enhanced up to room temperature. Their use would advance the process towards practical AFM spintronics.

The controlled transformation of materials, both their structure and their physical properties, is key to many devices. Ionic liquid gating can induce the transformation of thin-film materials over long distances from the gated surface. Thus, the mechanism underlying this process is of considerable interest. Here we directly image, using in situ, real-time, high-resolution transmission electron microscopy, the reversible transformation between the oxygen vacancy ordered phase brownmillerite SrCoO2.5 and the oxygen ordered phase perovskite SrCoO3. We show that the phase transformation boundary moves at a velocity that is highly anisotropic, traveling at speeds ~30 times faster laterally than through the thickness of the film. Taking advantage of this anisotropy, we show that three-dimensional metallic structures such as cylinders and rings can be realized. Our results provide a roadmap to the construction of complex meso-structures from their exterior surfaces.