Magnetic behavior of Sm 3+ in SmAsO 4: an experimental and theoretical study

Abstract

Samarium arsenate single crystals were grown by flux technique. The principal susceptibilities ( χ ‖ and χ ⊥) of the uniaxial system were measured in the temperature range 300–13 K. The room temperature anisotropy obtained from absolute measurements was checked by measuring the anisotropy directly. The magnetic anisotropy is not appreciable; the value of (Δ χ/ χ av) at 300 K is only 0.024. Because of the slow rise of the susceptibilities ( χ ‖ and χ ⊥) with the lowering of temperature the average susceptibility ( χ av) cannot be accounted for by the Curie–Weiss law. The smooth variation of the susceptibilities down to 13 K rules out any structural phase transition or symmetry breaking. An analysis of the observed results undertaken for the first time invoking crystal field (CF) theory based on the rare-earth site symmetry D 2d provides a satisfactory explanation to the experimental results; ordering effects of any consequence are absent. g-factors and the electronic heat capacity were computed theoretically. Various hyperfine properties, including the thermal variation of the Mössbauer spectra, were computed for both isotopes of Samarium ( 147 Sm and 149 Sm ) in the light of the proposed CF.