Effect of Li/Na Doping on Spin-Phonon Coupling in Camn2o4

Abstract

We have studied the magnetic and vibrational properties of polycrystalline compounds of Ca1-x(Li/Na)xMn2O4 (x = 0.1 and 0.2), grown by the solid-state reaction method. From X-ray diffraction results, all the compositions are identified to be stable in orthorhombic structure processing Pbcm crystal symmetry. Magnetic studies revealed para-to-antiferromagnetic phase transition at TN ~ 220 K for all the compositions. Two of the phonon modes, related to Mn/Mn-O vibrations exhibit anomalous behaviour below TN, stemming from the interaction of spins and phonons, showing a systematic trend with doping (Li/Na). The estimated spin-phonon coupling constant is in the range of 0.6 - 1.9 cm-1.

Keywords: Antiferromagnets, Raman spectroscopy, Spinels, Spin-phonon coupling