Magnetic properties of Fe/Tb multilayers with large Fe layer thickness

Abstract

Fe/Tb multilayers that display significant perpendicular magnetic anisotropy (PMA) up to an Fe layer thickness of 55 Å have been fabricated and examined for the first time (to the best knowledge of the authors). Two series of Fe/Tb multilayer samples with a wide range of Fe layer thickness ranging between 8 and 55 Å and with constant Tb layer thickness of 6.5 and 11.5 Å were fabricated by planar magnetron sputtering. The magnetic and structural properties of these samples were examined using x-ray diffraction, Mössbauer spectroscopy, and torque magnetometry. Mössbauer spectra show PMA of the Fe magnetic moments for samples that consist of Fe layers and mixed interfaces only. The formation of an unmixed Tb layer starting at about 12 Å Tb layer thickness leads to parallel alignment of the Fe magnetic moments. PMA in such multilayers is induced by a mixed interface and maintained by the exchange interaction between adjacent Fe layers. The interfaces that induce PMA in Fe/Tb multilayers are very close in composition to that of TbFe2 for which maximum PMA was found in thin amorphous Fe–Tb films.