The effective magnetoelectric coefficients of polycrystalline Cr2O3 annealed in perpendicular electric and magnetic fields

Abstract

Magnetoelectric annealing is necessary to remove antiferromagnetic domains and induce macroscopic magnetoelectric effect in polycrystalline magnetoelectric materials, and in this paper, we study the effective magnetoelectric properties of perpendicularly annealed polycrystalline Cr 2 O 3 using effective medium approximation. The effect of temperatures, grain aspect ratios, and two different types of orientation distribution function have been analyzed, and unusual material symmetry is observed when the orientation distribution function only depends on Euler angle . Optimal grain aspect ratio and texture coefficient are also identified. The approach can be applied to analyze the microstructural field distribution and macroscopic properties of a wide range of magnetoelectric polycrystals.

Large linear magnetoelectric effect and field-induced ferromagnetism and ferroelectricity in DyCrO4

“…To probe the off-diagonal nonzero components of the ME tensor α ME of the polycrystalline sample, we employ an ME annealing procedure with an H⊥E configuration, as described in the "Materials and methods" section and reported in the literature 31,32 . In a polycrystalline sample with a random distribution of the grain orientation, such an ME annealing procedure can be used to choose one of the ME domains for each grain so that the macroscopic ME effect can be observed considering the symmetry requirement.…”

Magnetism and Magnetoelectricity of Textured Polycrystalline Bulk Cr2O3 Sintered in Conditions Far out of Equilibrium

“…In contrast to single crystals and textured thin films, there are no reports on the spintronic performance of devices based on cost-efficient polycrystalline bulk Cr 2 O 3 . To this end, it is known that a hot-pressed polycrystalline Cr 2 O 3 material reveals a sizable magnetoelectric effect, which is only about 3 times smaller than the one of a single crystal. − We would like to note that the symmetry of the magnetoelectric (ME) effect does not allow the ME tensor average to be zero for powders independently of the presence or absence of the preferred texture. For example, for the random distribution of grains in the powder and parallel electric and magnetic fields, the ME effect in Cr 2 O 3 is isotropic .…”

“…More recent theoretical models, which take into account intergrain interaction and assume the Gaussian distribution of the orientation distribution function, allow one to obtain a good coincidence between analytics and experimental data. In particular, the longitudinal and transversal components of the ME tensor are reduced and enhanced, respectively. , Although a sizable ME coefficient is relevant for spintronic devices, by now, polycrystalline bulk materials are not implemented in spintronics research. For instance, it is not demonstrated yet that polycrystalline bulk Cr 2 O 3 can be fabricated in a quality that is sufficient for all-electrical readout of the antiferromagnetic order parameter as would be needed for practical applications in spintronics.…”