MAGNETIC-PROPERTIES OF A LAYERED AND ANISOTROPIC RHOMBOHEDRAL COMPOUND - BI-2(1-X)GD2XTE3

The paramagnetic resonance absorption spectra of Bi-2(1-x) Gd-2x Te-3 grown by the Bridgman technique have been measured at room temperature . The magnetization measurements have been performed in magnetic-field intensities up to 65 kOe at temperatures of 1.8, 4.2, 16, and 25 K. T he EPR data show that the Gd3+ site has a C-3v symmetry, indicating a true substitution of Bi3+ atoms by Gd3+. The curve fitting of the magn etic-field dependence of the magnetization has been performed using a Brillouin function representing isolated magnetic ions. An extra term was introduced to represent the contribution of the pairs. The results indicate a weak antiferromagnetic coupling between the Gd3+ ions. Thi s is similar to the one found in the case of Pb-1-x Gd-x Te. The bond lengths as well as the bond angles in the case of Bi-2((1-x)) Gd-2x Te -3 and Pb-1-x Gd-x Te are compared. The similarity of the J(p)/k(B) va lues (-0.5 K) in the two systems is explained in terms of superexchang e interaction via anions between Gd3+.