Physica B 253 (1998) 142—147 Magnetic properties in amorphous Co  Tb  Zr  thin films H. Ouahmane, H. Lassri*, A. Itri, A. Khmou, G. Suran  De & partement de physique, Universite & Moulay Ismaı ( l, Faculte & des sciences et techniques, d+Errachidia, Boutalamine B.P. 509 Errachidia, Morocco  LPS, Universite & Moulay Ismaı ( l, Faculte & des sciences de Meknes, B.P. 4010, Morocco  LPMME, Universite & Hassan II, Faculte & des sciences Ain chok, Maa L rif, B.P. 5366, Route d’E1 Jadida, km 8, Casablanca, Morocco  LPM, Universite & Mohammed V, Faculte & des sciences, avenue Ibn Batouta, B.P. 1014, Rabat, Morocco  Laboratoire de Magnetisme de Louis. Ne & el, CNRS, Av. des Marthyrs B.P. 38042 38 Grenoble 9 Cedex, France Received 22 January 1997; received in revised form 17 February 1998 Abstract Amorphous Co  Tb  Zr  thin films with a well-defined in-plane uniaxial anisotropy were prepared by RF sputtering. The saturation magnetization 4M  , the uniaxial anisotropy constant K  and the coercive field H  were studied as a function of temperature and for the composition range 0(X(7. The Tb moment at 4.2 K is found to be 9  in agreement with the theoretical value. This would indicate a collinear spin structure for Tb. The mean-field theory has been used to explain the temperature dependence of the magnetization. The exchange interactions between Co—Co and Co—Tb atom pairs have been evaluated. K  and H  are related by the equation H  "K  /  M  with the fitting parameters  and n.  1998 Elsevier Science B.V. All rights reserved. Keywords: Co  Tb  Zr  ; Thin films; Magnetic properties 1. Introduction Amorphous ferromagnetically soft thin films containing rare earth metals are of interest due to their industrial applications. The films are also in- teresting from a scientific point of view as they offer the possibility to study various aspects of 3d and 4f magnetism. Contrary to crystalline materials these aspects can be investigated in a continuous concen- tration of the rare earth metal as well as in relation * Corresponding author. with the low local symmetry that is characteristic for the amorphous state. Rare earth metal atoms with spin—orbit interaction are known to give rise to large random anisotropy in amorphous films [1]. Amorphous films can exhibit fairly low values of the coercive field H  , much smaller than 1 Oe [2,3]. The magnitude of H  is generally related to the overall composition of the films and the depos- ition parameters used. The main intrinsic para- meters which affect the value of the H  are the uniaxial anisotropy, the saturation magnetization and the microstructure which may lower or in- crease the coercive field. In this work we describe 0921-4526/98/$ — see front matter  1998 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 4 5 2 6 ( 9 8 ) 0 0 3 6 5 - 2