Local probe studies of Fe hyperfine field in CaFe_2As_2 by time differential perturbed angular distribution (TDPAD) spectroscopy and ab initio methods

摘要

Applying the γ-ray perturbed angular distribution technique we have measured the magnetic hyperfine field and spin relaxation time of recoil implanted ~(54)Fe in single and polycrystalline CaFe_2As_2 over the temperature range 20-360 K, encompassing both tetragonal and orthorhombic structural phases of the material. The magnetic response of Fe in the high temperature tetragonal phase (T ≥ 180 K), show Curie-Weiss type local susceptibility and Korringa like spin relaxation, reflecting the presence of localized moment on Fe. In the orthorhombic phase, the spin rotation spectra of ~(54)Fe show two magnetic hyperfine field components, both exhibiting quasi two dimensional magnetic ordering. The experimentally measured hyperfine field and Fe moment show good agreement with results obtained from ab initio calculations performed within the frame work of local spin density approximation (LSDA).