Investigation of ferromagnetic spinel semiconductors by hyperfine interactions of implanted nuclear probes

Abstract

The semiconducting ferromagnetic spinel compounds CdCr2Se4, CdCr2S4, HgCr2Se4 and CuCr2Se4 (metallic) were investigated by the perturbed angular correlations (PAC) method with the radioactive probes 111In, 111mCd, 111Ag, 117Cd, 199mHg and 77Br. The probes were implanted at the ISOLDE on-line separator (CERN-Geneva) into single crystals. From the time dependence of the PAC spectra and the measured hyperfine interaction parameters: electric field gradient and magnetic hyperfine field, the probe positions and the thermal behavior of the probes could be determined. Cd, Ag and Hg are substituted at the A-site, In at the A- and B-site in the semiconducting compounds and Br at the anion position. Electric and magnetic hyperfine fields were used as test quantities for theoretical charge and spin density distributions of LAPW calculations (WIEN97).