Interplay between Co-3d and Ce-4f magnetism in CeCoAsO

TL;DR

This study investigates the magnetic properties of CeCoAsO, revealing ferromagnetic order at 75 K, complex low-temperature anomalies, and microscopic insights into Ce-4f and Co-3d interactions using magnetization, specific heat, and NMR techniques.

Contribution

It provides a detailed analysis of the interplay between Ce-4f and Co-3d magnetism in CeCoAsO using multiple experimental methods, highlighting the microscopic magnetic behavior and low-temperature anomalies.

Findings

Ferromagnetic order at approximately 75 K.

Complex Schottky anomaly observed at 6.5 K.

Strong shift anisotropy in NMR spectra and evidence of weak Ce-Ce correlations.

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, $T_\mathrm{C}$=75 K. No further transitions are found down to 2 K. At 6.5 K a complex Schottky type of anomaly shows up in the specific heat results. The interplay between Ce-4f and Co-3d magnetism being responsible for that anomaly is discussed. Furthermore $^{75}$As NMR investigations have been performed to probe the magnetism on a microscopic scale. As-NMR spectra are analysed in terms of first and second order quadrupolar interaction. The anisotropic shift component $K_{\mathrm{ab}}$ and $K_{\mathrm{c}}$ could be derived from the $^{75}$As powder spectra. Towards lower temperature a strong shift anisotropy was found. Nonetheless $K_{\mathrm{iso}}$ 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 of $C/T$ towards lower temperatures supports this interpretation.