The role of the interface for perpendicular magnetic anisotropy of iron/terbium and iron/gadolinium multilayers

Ferromagnetic multilayers showing perpendicular magnetic anisotropy (PMA) can be used as information storage materials with significantly increased storage density compared to materials currently used. A detailed knowledge of the mechanism that creates PMA and the impact of different parameters on the magnetic properties in such multilayers is essential. 26 Fe/Tb and 11 Fe/Gd multilayer samples with a wide range of thicknesses were fabricated by planar magnetron sputtering. The other fabrication parameters besides thickness were left constant as far as possible. The magnetic and structural properties of these samples were examined using x-ray diffraction, Mossbauer spectroscopy and torque magnetometry. This study attempts to explain the PMA in multilayers of Fe and Gd or Tb. It has been found that the magnetic ordering in such multilayers is induced by a mixed interface very close in composition to that of amorphous thin alloy films of the constituent elements that show maximum PMA. The other important factor determining the magnetic properties of these multilayers is an exchange interaction between adjacent Fe layers. The thickness of the interface and the thickness of the particular layers of the constituent elements determine the alignment of the magnetic moments in such multilayers. No significant difference in the magnetic and structural properties between Fe/Tb and Fe/Gd multilayers could be measured.