Magnetic susceptibility of Fe/Cu multilayers: Ferromagnetic, antiferromagnetic, and spin-glass phases

In this work we present low-field magnetic measurements on multilayers of Fe 1.5 nm and Cu 1.5 nm layers, repeated 10 times, grown on Si(111) and Fe 5 nm/CaF2 40 nm/Si(111) substrates. Magnetic characteristics of a spin-glass phase are exhibited by samples directly grown on Si(111), for which the glass temperatures (T-G) depend strongly on the magnetic field, Above T-G those samples exhibit a ferromagnetic behavior. In contrast, samples grown on Fe/CaF2 buffer structure also show the spin-glass characteristics, but are antiferromagnetic above T-G. This work deals with the fundamental role played by the interface between Fe and Cu for these effects, which is clearly emphasized by the experimental results. (C) 1998 American Institute of Physics. [S0021-8979(98)46011-0].