Ferromagnetic-phase transition in the spinel-type CuCr2Te4

Ferromagnetic-phase transition in spinel-type CuCr2Te4 has been clearly observed. CuCr2Te4 is a telluride-spinel with the lattice constant a=11.134 a*, which has been synthesized successfully. The heat capacity exhibits a sharp peak due to the ferromagnetic-phase transition with the Curie temperature TC=326 K. This value of TC corresponds exactly to that of the negative peak of dM/dT in low field of 1.0Oe. The magnetic susceptibility shows the Curie-Weiss behavior between 380 and 650K with the effective magnetic moment μeff=4.14 μB/Cr-ion and the Weiss constant &thetas;=+357 K. The low temperature magnetization indicates the spin-wave excitations, where the existence of first term of Bloch T3/2 law and the next T5/2 term are verified experimentally. This spin-wave excitation is detected up to approximately 250K which is a fairly high temperature

Pressure Effect on Transport Properties of EuNi(Si1-xGex)3 Compounds

AbstractThe compounds of EuNi(Si1−xGex)3 order antiferromagnetically. At the temperature TC below the Ńeel temperature TN, EuNiSi3 (x = 0) shows an additional magnetic transition into ferro-magnetic state. TN decreases monotonously with increasing the Ge composition x. The Curie temperature TC decreases rapidly with increasing x and vanishes at the critical composition x ≈ 0.3. We have measured the electrical resistivity and thermopower of EuNi(Si0.8Ge0.2)3, which is a compound near to the boundary between the ferromagnetic and antiferromagnetic ground states in the phase diagram for EuNi(Si1−xGex)3 system, under pressures up to 1.8GPa at temperatures from 2 to 300K. The anomalies in ρ(T) and S(T) curves of EuNi(Si0.8Ge0.2)3 are observed at TC = 16K and TN = 34K at ambient pressure. Both TC and TN increase linearly with increasing pressure. The temperature variations of ρ and S of EuNi(Si0.8Ge0.2)3 at P = 1.8GPa are almost the same as those of EuNi(Si0.9Ge0.1)3 (x=0.1) at ambient pressure, revealing that the effect of pressure on TN and TC is the same as that of the increase of Si concentration. The pressure and atomic composition dependences of the magnetic transition temperatures TN and TC can be expressed by using the Grüneisen parameters. These results indicate that the changes of TN and TC are attributed to the change of atomic volume induced by the applying pressure or the atomic substitution

Hall Effect in Rare Earth Intermetallic Compounds TbAg_<1-x>In_x

The Hall effect has been observed on the polycrystals of rare earth intermetallic compounds TbAg_In_x in the paramagnetic temperature range. The ordinary Hall coefficients R_0 are positive for all compounds and these values cannot be interpreted satisfactorily by the free electron model. The spontaneous Hall coefficients R_s are larger by about three orders of magnitude than the values of R_0. It is shown that R_s depends strongly on the residual reristivity for the compounds which has x larger than 0.1