On the origin of KUin amorphous RE-TM magnetooptic recording materials

Exchange anisotropy was recently proposed as the origin of uniaxial perpendicular anisotropy in some RE-TM thin films. This magnetic anisotropy arises from the exchange interaction between the ferrimagnetic matrix and acicular shaped single domain ferromagnetic regions. Rotational hysteresis measurements on GdCo films show a non-vanishing value of the rotational magnetic hysteresis for magnetic fields greater than the magnetic anisotropy field (Hk). Such a behavior, first discovered in Co-CoO, is a necessary but not a sufficient condition for exchange anisotropy. The origin of the intrinsic uniaxial magnetic anisotropy energy density (Ku) in amorphous rare earth-transition metal (RE-TM) thin films has been attributed to pair ordering, single ion anisotropy, columnar structures that occur in the sputtering process, stress between the film and the substrate, and exchange anisotropy.