Interplay between Co3d and Ce4f magnetism in CeCoAsO

Abstract

We have investigated the ground-state properties of polycrystalline CeCoAsO by means of magnetization, specific heat, and solid-state NMR. Susceptibility and specific-heat measurements suggest a ferromagnetic order at about, TC =75 K. No further transitions are found down to 0.5 K. At 6.5 K a complex Schottky type of anomaly shows up in the specific-heat results. The interplay between Ce4f and Co3d magnetism being responsible for that anomaly is discussed. Furthermore A 75 s -NMR investigations have been performed to probe the magnetism on a microscopic scale. As-NMR spectra are analyzed in terms of first and second-order quadrupolar interaction. The anisotropic shift component Kab and Kc could be derived from the A 75 s powder spectra. Towards lower temperature a strong shift anisotropy was found. Nonetheless Kiso tracks the bulk susceptibility down to T=50 K very well. Furthermore the presence of weak correlations among the Ce ions in the ferromagnetic state is discussed. The observed increase in C/T towards lower temperatures supports this interpretation. © 2010 The American Physical Society.