INVESTIGATION OF CUXGAYCRZSE4 SINGLE-CRYSTALS

From X-ray photoelectron spectroscopy data and X-ray microprobe analys is the formula CuxGayCrzSe4 (x + y + z approximate to 3) for the inves tigated single crystals was determined. Replacement of Cu by Ga in tet rahedral sites of the spinel-type structure was observed. A negative c hemical shift of the Cu 2p levels as well as an absence of Cu shake-up satellite lines was noticed. T-c dependency on the Ga content was fou nd from susceptibility measurements. Effective and saturation magnetic moments at low concentrations of gallium (y < 0.16) were found to be higher than in CuCr2Se4. For gallium-rich samples the values of the mo ments decrease rapidly. The problem of metal valency in this system is discussed in relation to charge distribution. Covalency and stability of the spinel-type structure is also discussed.