Magnetic properties of superparamagnet/ferromagnet heterostructures

J Balogh, M Csontos, D Kaptás, LF Kiss, Tamás Pusztai1, J Swerts, S Vandezande, K Temst, C Van Haesendonck, G Mihaly

1Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, P.O. Box 49, Budapest H-1525, Hungary

Fe(x)/Ag(2.6 nm) multilayer heterostructures containing Fe
layers of periodically altered thickness have been prepared by
molecular beam evaporation to study the influence of
ferromagnetic layers on the magnetic properties of granular
multilayers. The magnetic properties were examined by SQUID
magnetization measurements and Mossbauer spectroscopy, and the
magnetoresistance was measured in parallel and transversal
magnetic fields up to 12 T. Samples with x = 0.2 and 1.5 nm were
prepared both as separated and as interleaved multilayer
heterostructures. The average blocking temperature of the
granular Fe layers (x = 0.2 nm) is not altered when the
thickness of every fourth layer is increased to 1.5 nm. On the
other hand the temperature dependence of the magnetoresistance
was found to be significantly different for the separated and
the interleaved samples.