Synthesis, structural and magnetic studies of the CuCr1-xRhxO2 delafossite solid solution with 0 ≤ x ≤ 0.2

The CuCr1-xRhxO2 series is investigated by X-ray diffraction, magnetization measurements and Raman spectroscopy on ceramic samples. It is found that a delafossite solid solution is maintained up to x = 0.2 in CuCr1-xRhxO2. The small observed variation in cell parameters is consistent with the small difference between the ionic radii of Cr3+ and Rh3+. A significant broadening of X-ray reflections is observed and when analyzed using the Williamson-Hall relationship showed that the strain generated by Rh substitution is strongly anisotropic, affecting mainly (Cr,Rh)-O bonds in the ab plane. Room temperature Raman spectra displayed three main Raman active modes. All modes shift to lower frequency and undergo significant changes in intensity with increasing Rh content, showing the effect of Rh atoms on the M3+-O bond strength. The magnetic behavior of CuCr1-xRhxO2 samples was investigated as a function of temperature and applied field. At high temperature paramagnetic behavior, and at low temperature, evidence for weak ferromagnetism, reinforced by a hysteresis loop at 4 K is observed. The magnetic behavior of CuCr1-xRhxO2 is attributed to the disorder of Cr and Rh in octahedral sites resulting in short-range Cr-O-Cr and Cr-O-Rh interactions, which give rise to short-range weak ferromagnetism. (C) 2011 Elsevier Ltd. All rights reserved.