Magnetic domains and unusual hysteresis loops of yttrium iron garnet crystals revealed by magneto-optic effects

X D Zhu

doi:10.1063/5.0054528

Abstract

I present a magneto-optic effect study of magnetic domains in a ferrimagnetic yttrium iron garnet crystal at different stages of a hysteresis loop. By measuring the Faraday effect in response to the out-of-plane component and Kerr effects to the in-plane components of the sample magnetization, I examined the evolution of magnetic domains during a hysteresis loop in an in-plane external magnetic field. I found that crystalline anisotropy, magneto-static energy, and the presence of movable domain walls play indispensable roles in the domain orientation, particularly when the external field is near zero, and have led to seemingly unusual appearances of hysteresis loops.

Highlights

Ferromagnetic and ferrimagnetic states are important phases of solids
With the information on magnetization components along the other two directions, I can attribute the unusual shapes of these hysteresis loops to the often-neglected effect of magneto-static energy, which is enabled by movable domain walls in the yttrium iron garnet (YIG)(100) sample
With all three components of the YIG(100) sample magnetization measured during a hysteresis loop, what do we learn as to what happens in the sample as the field sweeps up and down? Can we understand unusual shapes of the hysteresis loops displayed in Fig. 3? What can one expect, in general, when a hysteresis loop is measured on a single crystal sample that contains a number of spatially uncharacterized domains?

Summary

INTRODUCTION

Ferromagnetic and ferrimagnetic states are important phases of solids. They are present in many materials of practical utility and in new quantum materials, often at low temperatures or under high pressures. Domains with different magnetic orientations and separated by movable domain walls can be formed even within a homogeneous region of a sample. This is driven by the propensity to the lowest total free energy configuration, especially when the external field is weak or absent. Spatially resolved magnetic measurements are needed and should be performed, when feasible This facilitates efforts to understand mechanisms that lead to ferromagnetic states and intrinsic characteristics and to connect these intrinsic properties with the averaged behaviors of a sample as a whole. With the information on magnetization components along the other two directions, I can attribute the unusual shapes of these hysteresis loops to the often-neglected effect of magneto-static energy, which is enabled by movable domain walls in the YIG(100) sample

EXPERIMENTAL PROCEDURES

DISCUSSION

CONCLUSION