Electrical, magnetic, and EPR studies of the quaternary chalcogenides Cu 2AIIBIVX4 prepared by iodine transport

Abstract

Electrical, magnetic, and electron paramagnetic resonance (EPR) measurements have been made on crystals and powders of several quaternary chalcogenides of the type Cu 2 A II B IV X 4, where A II = Zn, Mn, Fe, or Co, B IV = Si, Ge, or Sn, and X = S or Se. The electrical properties of these compounds are extrinsic, but their magnetic properties do not appear to be affected by impurities. The magnetic moments of the Cu 2Mn BX 4 compounds decrease with increasing covalency of the Mn X bond, and those of Cu 2FeGeS 4 and Cu 2CoGeS 4 reflect an orbital contribution to the moment. Both the Weiss constants and magnetic ordering temperatures in these compounds show an evolution from antiferromagnetism to ferromagnetism with increasing separation between the moments. Magnetic measurements on single crystals of Cu 2MnGeS 4, Cu 2CoGeS 4, and Cu 2FeGeS 4 indicate that only the latter is anisotropic. EPR measurements on crystals and powders of Cu 2ZnGeS 4 doped nominally with 0.1% Mn reveal that Mn 2+ experiences an axial distortion and that the bond ionicity is the same as in ZnS.