Multilayer Permalloy films grown by molecular-beam epitaxy

Abstract

Single and multilayer [111]-textured films of Permalloy and Cu were grown by molecular-beam epitaxy (MBE) on (111) Si substrates. The magnetic properties of the films were measured by ferromagnetic resonance and M-H loop tracer. The microstructure was observed by transmission electron microscopy, reflection high-energy electron diffraction, and x-ray diffraction. Even the single-layer films had lower easy axis coercivity Hce (≊0.6 Oe) and a lower in-plane anisotropy field (≊1.1 Oe) than permalloy films of similar thickness (≊80 nm) deposited by sputtering. In these single-layer films, the grain size and Hce both increased with improved pre-MBE cleaning of the Si substrate. The multilayers consisted of five identical thickness Permalloy layers separated by Cu interlayers. Multilayers with total magnetic thickness greater than 100 nm exhibited lower Hce than equivalent single-layer films. 4πMs, measured by a combination of ferromagnetic resonance and M-H loop tracer in very thin (<5 nm) permalloy layers was found to drop off relative to the bulk value of 9.5 kG; a value of 5.0 kG was measured for a multilayer with 1-nm-thick Permalloy layers.