a b s t r a c tMagnetic susceptibilities of Eu 2 O 3 , EuF 3 and EuBO 3 have been measured over the wide temperature range 5-650 K. The Van Vleck paramagnetism, with the ground state of 7 F 0 (S ¼ 3, L¼ 3), has been investigated comprehensively. The temperature independent paramagnetism emerges manifestly below approximately 100 K. The variation of the susceptibility with temperature for EuBO 3 is in satisfactory agreement with the coupling constant l ¼ 471 K, where the spin-orbit interaction is lL Á S for the Russell-Saunders coupling on the basis of Van Vleck theory with one parameter l. The value of l ¼ 490 K can fit the susceptibility data of EuF 3 . The deviation from the theory arises in Eu 2 O 3 . This discrepancy originates mainly from the influence of the crystalline field. Susceptibility of Gd 2 O 3 , having the ground state of 8 S 7/2 (S ¼ 7/2, L ¼0), is also presented as a magnetic standard compound in comparison with these results.

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Ferromagnetic phase transition in spinel-type CuCr 2 Te 4 has been clearly observed. CuCr 2 Te 4 is a telluride-spinel with the lattice constant a = 11.134 Å, which has been synthesized successfully. The heat capacity exhibits a sharp peak due to the ferromagnetic phase transition with the Curie temperature T c = 326 K. This value of T c corresponds exactly to that of the negative peak of dM/dT in low field of 1.0 Oe. The magnetic susceptibility shows the Curie-Weiss behavior between 380 and 650 K with the effective magnetic moment µ eff = 4.14 µ B per Cr-ion and the Weiss constant Ө = 357 K. The low temperature magnetization indicates the spin-wave excitations, where the existence of first term of Bloch T 3/2 law and the next T 5/2 term are verified experimentally. This spin-wave excitation is detected up to approximately 250 K which is fairly high temperature.

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