Uniaxial in-plane magnetic anisotropy and exchange bias in Sm/Fe bilayers

We have studied structural and magnetic properties of quartz/Sm(25 nm)/Fe(1 5 nm) thin films by grazing incidence x-ray diffraction, atomic force micro scopy, longitudinal magneto-optic Kerr effect, and superconducting quantum interference device magnetometry. Both Sm land Fe layers exhibit growth in a preferential direction with textured granular structure. The Fe layer is composed of small elongated grains (36 nm long and 21 nm wide). The Fe grai ns are monodomains and are all parallel aligned due to the texture effect. Therefore, their magnetic shape anisotropy is summed, producing a final uni axial in-plane magnetic anisotropy in the film. The Sm/Fe system is an anti ferromagnetic/ferromagnetic bilayer exhibiting exchange bias coupling below 40 K. The long-range character of Sm-Fe spin interaction located near the interface maintains this coupling, in spite of disorder effects at the inte rface, such as Sm-Fe alloying, and results in a power-law decay with temper ature for the exchange bias field(H-E). [S0163-1829 (99)09025-6].