Ferrimagnetic insulators for spintronics: Beyond garnets

Abstract

Ferrimagnetic insulators have gained much attention as material platforms with efficient magnetization dynamics. To date, epitaxial iron garnet thin films are the most widely used materials in the emerging field of “insulator spintronics.” However, further advances in this field require overcoming the disadvantages of garnets—e.g., their complex structure, high growth temperature, incompatibility with other crystalline materials, and relatively weak perpendicular magnetic anisotropy. In this Perspective, we make the case that epitaxial thin films of spinel ferrites and hexagonal ferrites are viable materials for insulator spintronics with complementary advantages over the oft-used garnets. Specifically, spinel ferrites have a simpler structure, can crystallize at lower temperatures, and are more amenable to coherent integration with various materials; hexagonal ferrites possess enormous perpendicular anisotropy of bulk origin, in contrast to garnets where the strength of anisotropy is restricted by interfacial strain. The expanded repertoire of materials for insulator spintronics will enable new physical insights and potential applications, beyond what is currently possible with garnets.