Tunable enhancement of magnetization dynamics by selection of the crystallographic orientation of the hybrid interface of exchange-coupled α−Fe2O3 /permalloy heterostructures

We investigate spin dynamics in α−Fe2O3/Ni80Fe20 (Py) heterostructures, uncovering a robust mechanism for designing the ferromagnetic resonance (FMR) frequency through control of crystal orientation, temperature, and applied magnetic field. Employing cryogenic ferromagnetic resonance spectroscopy, we demonstrate that the relative orientation of the Néel vector of α−Fe2O3 and the magnetization of the Py layer is highly tunable across the Morin transition temperature (TM). Central to our findings is the pivotal role of crystal orientation in governing the spin dynamics, with the reorientation of the Néel vector serving as a complementary mechanism that further modulates the system's behavior. Our experiments and corroborating theoretical model reveal distinct resonance behavior for different crystal orientations, highlighting the pivotal role of the mutual Néel vector and magnetization geometry in dictating FMR frequencies. In this way, we can tune the FMR frequencies up to a tenfold increase by manipulating the mutual Néel vector/magnetization configuration. Our study comprises all common α−Fe2O3 crystal orientations and develops a unified theoretical description of the ensuing spin dynamics. Published by the American Physical Society 2025