AN X-RAY-DIFFRACTION AND MAGNETIC-SUSCEPTIBILITY STUDY OF YBXY2-XO3

Polycrystalline samples of the new semimagnetic semiconductor YbxY2-xO 3 (x = 0.06, 0.12, 0.25, 0.39, 1.00, 1.40, 1.80) were obtained by cera mic technology. An x-ray diffraction experiment was performed on all o f the samples at room temperature. These data provided the basis for R ietveld refinements. The refinements showed that Yb3+ ions preferentia lly occupy the 24d position. The lattice constants and the mean cation -anion distances decrease linearly with the Yb3+-ion concentration. Th e inverse magnetic susceptibilities for all of the samples depend line arly on the temperature for 4 K < T < 30 K. In this region only the lo west Kramer's doublet is populated, and for that level the effective m agnetic quantum number M-1eff. is deduced. The Curie-Weiss paramagneti c temperatures theta(x) obtained from the low-temperature region depen d linearly on the concentration x. Over the whole experimental region 4 K < T < 250 K, the magnetic susceptibility deviates from the Curie-W eiss law, and its calculation requires inclusion of the first excited Kramer's doubler. The effective magnetic quantum number M-2eff and ene rgy gap Delta W of the first excited doublet were deduced.