X-ray powder diffraction measurements and differential thermal analysis (DTA) were made on polycrystalline samples of the Cu 2 Cd 1−z Mn z GeSe 4 and Cu 2 Cd 1−z Fe z GeSe 4 alloy systems. The diffraction patterns were used to show the equilibrium conditions and to derive lattice parameter values. The effect of the annealing temperature and cooling rate to room temperature are discussed. For the Cu 2 Cd 1−z Fe z GeSe 4 system, only two single solid phase fields, the tetragonal stannite ␣ and the wurtz-stannite ␦ structures were found to occur in the diagram. For the Cu 2 Cd 1−z Mn z GeSe 4 system, in addition to the tetragonal stannite ␣ and the wurtz-stannite ␦ phases, MnSe was found to exist in the diagram. The DTA experiments showed that the cooling curves for both systems exhibited effects of undercooling.

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Measurements of low field static magnetic susceptibility and of magnetization with pulsed magnetic fields up to 32T 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 8.1K and shows a triple point at (7.8K, 2.2T). 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 5T show magnetothermal effects below 4.5K.

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