Single crystal growth and some properties of HgCr 2− xIn xSe 4 solid solutions

Abstract

Indium was found to substitute for Cr ions to a limited extent in the ferromagnetic spinel HgCr 2Se 4. For the solid solution HgCr 2− x In x Se 4, the maximum value of x was determined to be 0·45. The lattice parameter increases with increasing x from a 0=10·743 Å for x=0, to a 0=10·836 Å for x=0·45. The u-parameter is 0·390 for all compositions. The single crystals of HgCr 2− x In x Se 4 studied were all grown by chemical transport either from an HgCr 2− x In x Se 4−CrCl 3 system or from an HgCr 2 Se 4−CrCl 3−InCl 3 system. In the former system, the fractionation of In during crystal growth was quite marked in that the In content in the large single crystals was always significantly lower than in the polycrystalline powder. Attempts to grow single crystals with an In concentration near the solubility limit were not successful. The maximum lattice parameter obtained for single crystals grown by chemical transport was 10·777 Å, which corresponds to x=0·17. The Curie temperature of the HgCr 2− x In x Se 4 single crystals grown was found to be a monotonically decreasing function of the In content. The electrical resistivity of the single crystals grown had a maximum near the Curie temperature just as did the ‘In-doped’ HgCr 2Se 4 which had been previously grown by chemical transport from Hg 1− n In n Cr 3Se 4 powders ( y≤0·02) using CrCl 3 as a transport agent. The magnetoresistance of the single crystals was negative and had a maximum near T c , as was also the case for the ‘In-doped’ HgCr 2Se 4. However, the increase in resistivity from room temperature to T c for the present crystals was found to be markedly lower than for the ‘In-doped’ HgCr 2Se 4. indicating that for the system HgCr 2− x In x Se 4 the conduction is nearly metallic in the temperature range studied.