NMR properties of CoRhP: mixing between Co and Rh sites

Abstract

NMR properties of 59Co and 31P in CoRhP with orthorhombic TiNiSi structure are reported. Field-swept NMR spectra of 59Co show very broad ones from nonmagnetic Co sites where satellite peaks due to quadrupole interaction are smeared out. The Fourier transformed spectrum of 31P NMR has two peaks. It is suggested that the Co and Rh atoms do not order but their sites are mixed. The mixing is consistent with a Rietvelt analysis of X-ray diffraction powder patterns where a mixing of 10% of Co atoms into Rh sites is estimated. This kind of mixing seems to be one of the origins of the variety of magnetic and electric properties of MRuP and MRhP (M=3d transition metal) systems. The nuclear spin-lattice relaxation rates of 59Co and 31P in CoRhP obey Korringa relations at high temperatures and they show stepwise decreases with decreasing temperature at 11 K where the static susceptibility has a peak. The behaviors are interpreted as an onset of a charge density wave (CDW) at 11 K rather than an onset of an antiferromagnetism.