Mn-55 NMR study of the hexagonal Laves phase compound ThMn2: Coexistence of magnetic and nonmagnetic sites of Mn

The magnetic ground state of the hexagonal Laves phase intermetallic compou nd ThMn2 was investigated by Mn-55 nuclear magnetic resonance. Both paramag neticlike resonance at the zero-Knight-shift position and antiferromagnetic resonance at high frequencies were found to be consistent with the coexist ence of magnetic and nonmagnetic Mn atoms, i.e., an antiferromagnetic state with partially nonmagnetic Mn sites, proposed from neutron diffraction exp eriments. The hyperfine field at the magnetic 6h site was estimated to be 1 38 kOe, which is larger than that observed for another antiferromagnetic La ves phase compound YMn2 (114 kOe) despite the 6h-site magnetic moment estim ated by neutron diffraction experiments (16 mu(B)) being smaller than the m oment of YMn2 (2.7 mu(B),). Possible interpretations are discussed.[S0163-1 829(99)05821-X].