SPIN REORIENTATION AND EXCHANGE COUPLING IN THE DY1-XERXFE10SI2 COMPOUNDS

The structural and magnetic properties of Dy1-xErxFe10Si2 are investig ated. X-ray analysis reveals that these compounds are of the tetragona l ThMn12 structure. In this structure the rare earth atoms occupy one crystallographic position 2(a). The unit cell contains 26 atoms. The s pin reorientation temperature, T(SR), was measured from the temperatur e dependence of the initial susceptibility using an ac bridge of mutua l inductance of the Harsthorn type. Dy+3 and Er+3 have opposite contri butions to the entire magnetic anisotropy. The spin reorientation temp erature is found to be about 271 K in DyFe10Si2 and 48 K in ErFe10Si2. The values are discussed applying the crystal field model. The value of the rare earth-transition metal exchange coupling constant J(RFe)/k (B) derived from the mean-field model analysis of the Curie temperatur e is about -13 K. The Fe-Fe exchange integral is much higher and is eq ual to about 75 K.