Magnetic properties of ultrathin Co/Ge(111) and Co/Ge(100) films

The orientation of the magnetization and the occurrence of interfacial ferr omagnetic inactive layers for ultrathin Co films grown on Ge(111) and Ge(10 0) surfaces have been studied using the in situ surface magneto-optic Kerr effect. On a Ge(111) substrate, cobalt films (less than or equal to 28 mono layers) with in-plane easy axis of magnetization have been observed; howeve r, on a Ge(100) substrate, ultrathin Co films (14-16 monolayers) with cante d out-of-plane easy axis of magnetization were measured. The ferromagnetic inactive layers were formed due to the intermixing of Co and Ge and lowerin g the Curie temperature by reducing Co film thickness. The Co-Ge compound i nactive layers were 3.8 monolayers thick for Co films grown on Ge(111) and 6.2 monolayers thick for Co films deposited on Ge(100). This is attributed to the difference of the density of surface atoms on Ge(111) and Ge(100). ( C) 2001 American Institute of Physics.