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Measurements of low field static magnetic susceptibility and of magnetization with pulsed magnetic fields up to 32 T is made as a function of temperature on polycrystalline samples of the compound MnGa2Se4 which has a tetragonal structure. The resulting data is used to give information on the magnetic spin-flop and magnetic saturation transitions.

Measurements of low field static magnetic susceptibility and of magnetization with pulsed magnetic fields up to 32 T have been made as a function of temperature on polycrystalline samples of the compound MnGa2Se4 which has a tetragonal structure. The resulting data have been used to give information on the magnetic spin-flop and magnetic saturation transitions. It has been found that MnGa2Se4 has a zero-field Néel temperature TN of 8.1 K and shows a triple point at (7.8 K, 2.2 T). Details of the magnetic B-T phase diagrams were determined for the phases and the results compared with the predictions of theoretical uniaxial models. The susceptibility χ(T) curves for B=3 and 5 T show magnetothermal effects below 4.5 K. [ABSTRACT FROM AUTHOR]

X-ray powder diffraction study of the p-type semiconductor Cu[sub 2]SnSe[sub 4] shows that this material crystallizes in the cubic structure, space group F&4macr;3m, with unit cell parameter a=5.6846(3) Å. The temperature variation of the hole concentration between 120 and 300 K, obtained from the Hall effect and electrical resistivity measurements, is due to the thermal activation of an acceptor level with ionization energy of about 0.02 eV. The temperature variation of the hole mobility is explained by considering the scattering of charge carriers by ionized impurities and acoustic phonons. From this analysis, the density-of-states effective mass of the holes is estimated to be about 0.8 m[sub e], m[sub e] being the free electron effective mass. From the optical absorption spectra, the fundamental absorption edge is found to be direct. The value of the lowest energy gap and the spin-orbit splitting were estimated to be about 0.35 and 0.20 eV, respectively. The temperature dependence of the magnetization measurements shows that Cu[sub 2]SnSe[sub 4] is paramagnetic, indicating that most of the copper atoms have the divalent charge state. [ABSTRACT FROM AUTHOR]