55MnNMR study of the hexagonal Laves phase compoundThMn2: Coexistence of magnetic and nonmagnetic sites of Mn

Abstract

The magnetic ground state of the hexagonal Laves phase intermetallic compound ${\mathrm{ThMn}}_{2}$ was investigated by ${}^{55}\mathrm{Mn}$ nuclear magnetic resonance. Both paramagneticlike resonance at the zero-Knight-shift position and antiferromagnetic resonance at high frequencies were found to be consistent with the coexistence of magnetic and nonmagnetic Mn atoms, i.e., an antiferromagnetic state with partially nonmagnetic Mn sites, proposed from neutron diffraction experiments. The hyperfine field at the magnetic $6h$ site was estimated to be 138 kOe, which is larger than that observed for another antiferromagnetic Laves phase compound ${\mathrm{YMn}}_{2}$ (114 kOe) despite the $6h$-site magnetic moment estimated by neutron diffraction experiments $(1.6{\ensuremath{\mu}}_{\mathrm{B}})$ being smaller than the moment of ${\mathrm{YMn}}_{2} (2.7{\ensuremath{\mu}}_{\mathrm{B}}).$ Possible interpretations are discussed.