Hidden Magnetic States Emergent Under Electric Field, In A Room Temperature Composite Magnetoelectric Multiferroic

Abstract

The ability to control a magnetic phase with an electric field is of great current interest for a variety of low power electronics in which the magnetic state is used either for information storage or logic operations. Over the past several years, there has been a considerable amount of research on pathways to control the direction of magnetization with an electric field. More recently, an alternative pathway involving the change of the magnetic state (ferromagnet to antiferromagnet) has been proposed. In this paper, we demonstrate electric field control of the Anomalous Hall Transport in a metamagnetic FeRh thin film, accompanying an antiferromagnet (AFM) to ferromagnet (FM) phase transition. This approach provides us with a pathway to "hide" or "reveal" a given ferromagnetic region at zero magnetic field. By converting the AFM phase into the FM phase, the stray field, and hence sensitivity to external fields, is decreased or eliminated. Using detailed structural analyses of FeRh films of varying crystalline quality and chemical order, we relate the direct nanoscale origins of this memory effect to site disorder as well as variations of the net magnetic anisotropy of FM nuclei. Our work opens pathways toward a new generation of antiferromagnetic -ferromagnetic interactions for spintronics.In recent years, the ever increasing need for large scale data storage in computing systems has kindled significant interest in new materials and new physical phenomena that could lead to denser and more energy efficient memory systems. One approach is the heat assisted magnetic recording (HAMR) for which low Neel temperature AFMs have been suggested to play a key role 1 . In this context, the AFM to FM phase transition makes FeRh a serious contender for insertion into heterostructures utilizing exchange bias. Typically, in magnetic systems, defects impede domain wall motion, increase the coercivity, lower magnetization, and decrease spin polarization. Going beyond this traditional thinking, in this work we demonstrate that it is possible to exploit crystalline defects in FeRh to

Structural, magnetic, and transport properties of Fe1−xRhx/MgO(001) films grown by molecular-beam epitaxy

“…3(e), shows that the transition is sharp, hysteretic, and symmetric-attributes consistent with firstorder transitions-and occurs at 385 6 3 and 401 6 3 K during heating and cooling, respectively. The pronounced modulation in resistivity observed, Dq=q ðq AF À q FM Þ=q FM ¼ 80%, represents the highest thermally induced value reported 6,10,22,[43][44][45] and is consistent with the 85 6 6% theoretical maximum realizable for well-ordered films; 22 the narrow transition widths, DT ¼ 3 K, are the smallest observed to date. 6,10,11,22,[43][44][45] For bulk stoichiometric samples, a comparable resistivity change was observed at room temperature by driving the AF-FM transition with pulsed magnetic fields exceeding 15 T; thermally induced resistivity changes were not investigated, but a T c of 405 K, in close agreement with our measured values, was deduced from temperature-dependent heat capacity measurements.…”

Antiferromagnetic spintronics

“…Metallic metamagnets with an antiferromagnetic to ferromagnetic transition (such as FeRh) offer the possibility to indirectly operate the antiferromagnetic order via iterative steps consisting of manipulating the ferromagnetic order and undergoing the magnetic phase transition. In the case of FeRh, a small (noncrystalline) anisotropic magnetoresistance was also detected in the antiferromagnetic phase and quasistatic write-read operations were demonstrated (Marti et al, 2014;Moriyama, Takei et al, 2015;Clarkson et al, 2017). Other important materials include, for example, Gd alloys, such as GdSi, GdGe, and GdAu 2 (Tung et al, 1996).…”

Voltage‐Control of Magnetism in All‐Solid‐State and Solid/Liquid Magnetoelectric Composites

“…Afterward, Eerenstein et al [45] demonstrated the control of magnetization in similar LSMO/BTO epitaxial heterostructures using strain-controlled coupling induced by an external voltage. [96] Besides fully oxide systems, there has been a great interest in combining ferromagnetic metal films, [24][25][26] alloys, [58][59][60][61][97][98][99][100] and multilayers [101][102][103] with piezoelectric materials. The effect persisted even in case of an increase, removal, or reversal of the external voltage.…”