Field-Free Deterministic Magnetization Switching with Ultralow Current Density in Epitaxial Au/Fe₄N Bilayer Films

Abstract

Current-induced magnetization switching was investigated in Au/Fe₄N bilayer films grown by a plasma-assisted molecular beam epitaxy (PA-MBE) system. Depending on lattice distortion and interfacial coupling induced by substrates, the Fe₄N layer could be divided into two sublayers having different magnetic anisotropies. The bottom sublayer shows perpendicular magnetic anisotropy (PMA), while the top one has in-plane magnetic anisotropy (IMA). Coupling between the two sublayers provides an extra in-plane effective field and enables a field-free magnetization switching in the bilayer films. By summarizing a series of Hall measurements, a switching phase diagram was obtained. Temperature-dependent switching behaviors demonstrate that the threshold current density for the field-free magnetization switching, which is much smaller than that of pervious reports, increases with decreasing temperature and shows similar temperature dependences to those of coercivity.