Magnetocrystalline anisotropy of Ce2Co17-xAlx compounds with x = 0-3

An investigation of the structure and magnetocrystalline anisotropy of Ce2Co17-xAlx (x=0, 1, 2, and 3) compounds has been performed by means of x-ray diffraction and magnetization measurements. It is observed that the unit-cell volume, Curie temperature, and saturation magnetization of Ce2Co17-xAlx compounds are anomalously low in comparison with the values obtained from a simple extrapolation by the other R2Co17-xAlx compounds, such as R=Pr and Nd. These anomalies may be an evidence of a mixed-valence behavior of the Ce ion. X-ray diffraction measurements on magnetically aligned Ce2Co17-xAlx powders with x=0-3 exhibit an easy-axis type of magnetic anisotropy at room temperature. Substitution of Al for Co leads to a change of the magnetocrystalline anisotropy of the Co sublattice from the basal plane to c axis and strongly increases the uniaxial anisotropy of Ce2Co17-xAlx. The magnetocrystalline anisotropy field H-A is found first to increase and then decrease with increasing Al concentration, attaining a maximum value of 18 kOe at x=2. The magnetocrystalline anisotropy constant K-1 shows a small decrease with increasing temperature and K-2 is almost a constant. (C) 1999 American Institute of Physics. [S0021-8979(99)56308-1].Physics, AppliedSCI(E)CPCI-S(ISTP)