The structural and magnetic properties of Sr-doped multiferroic CaMn7O12

Abstract

The structural and magnetic properties of Sr-doped multiferroic [Formula: see text] were investigated by X-ray diffraction (XRD), Raman spectra, X-ray absorption spectroscopy and temperature dependence of magnetization. The XRD indicates that the samples are rhombohedral lattice (space group [Formula: see text]) with small additional phase [Formula: see text]. The refined lattice parameters of the main phase increases by the Sr doping. The Raman spectra demonstrate the phonon vibration direction is affected, which is probably due to the rotation of [Formula: see text] octahedral. However, as the valence state of Sr and Ca is same at +2, the samples with doping show nonvariation of peak position at Mn [Formula: see text] X-ray absorption spectra, indicating that the ratio of [Formula: see text] and [Formula: see text] ions is unchanged. And the magnetic transition temperature both at [Formula: see text] and [Formula: see text] is also not tunable because the amount of magnetic interaction between [Formula: see text] and [Formula: see text] is not influenced by doping Sr ion. Only the enhancement of the magnetization at low temperature is observed, which is the same as the effect caused by external magnetic fields. An unsaturated wasp-waist type hysteresis loop is observed, indicating the competition between ferromagnetic-like and antiferromagnetic order.