Effects of Interface Properties on the Onset Thickness of Ferromagnetism in the Co/InP Hybrid System

Abstract

We have investigated the effects of interface structures on the magnetic properties of the Co/InP hybrid system by using in situ surface magneto-optical Kerr effects (SMOKE), scanning tunneling microscopy (STM) and Auger electron spectroscopy (AES). InP(001) substrates with different surface characteristics were prepared by using cycles of ion bombardment and annealing (IBA) method while varying the annealing temperature from 400 degrees C to 450 degrees C. The Co film begins to show a ferromagnetic hysteresis loop at a thickness of 2 mn of Co on the InP surface prepared at 400 degrees C. However, the Co film deposited on the InP surface prepared at 450 degrees C shows no ferromagnetic signal up to a Co thickness of 16 mn. We observed from STM results that In droplets were produced when the InP substrate was annealed at temperatures higher than 400 degrees C during the IBA processes. The AES depth profile shows that interdiffusion between Co and In increases as the density of In droplets increases. These In droplets strongly interact with Co atoms and play a crucial role in the onset thickness for ferromagnetism in Co films.