INDUCED ANISOTROPY IN AMORPHOUS CO-ZR-M (M = ZR,NB,TI) AND CO-ZR-PT THIN-FILMS - A MAGNETIC AND A STRUCTURAL STUDY

A magnetic and structural investigation was carried out on Co95-xZr5Mx (M=Zr, Nb, or Ti) and Co91-xZr9Ptx amorphous thin films in order to determine the physical origin of the induced in-plane uniaxial anisotropy K(u). The films were prepared by rf sputtering and the deposition was performed in a magnetic field. The variations of K(u) were studied as a function of the sputtering parameters, composition, concentration, the thermomagnetic treatment, and structural-relaxation process. As a result of these investigations a model for the origin of K(u) is advanced, which involves the single-ion anisotropy mechanism. K(u) is the sum of two contributions K(u)a+K(u)s where K(u)a and K(u)s are the induced anisotropies related to the local anisotropy of the octahedral-icosahedral and trigonal-type clusters, respectively. The number of trigonal clusters varies as a function of P(Ar) and thus explains the variation of K(u) with P(Ar). In Co-Zr-Pt an extra contribution to K(u) is observed due to the pseudodipolar ordering that results from the magnetic polarization of Pt. Co-Zr-Pt films exhibit a peculiar thermomagnetic relaxation that is explained by the reversibility of the pseudodipolar anisotropy and the thermal instability of trigonal-type clusters resulting from the substitution of Pt.