Thermal, microstructural, optical, magnetic and magnetocaloric studies for Ni0.5Mn0.5Cr2O4 chromite spinel prepared using sol-gel method

Abstract

• The Ni 0.5 Mn 0.5 Cr 2 O 4 chromite spinel was prepared using sol-gel method. • The phase transformation for the sample was confirmed using TGA and DSC analyses. • The sample crystallizes in the cubic spinel structure with F d 3 ¯ m space group. • The prepared material has higher absorption of visible light in the photocatalytic reactions. • Magnetocaloric properties for the sample are quite comparable to several literature values found for other chromite spinels. In this work, the properties of the Ni 0.5 Mn 0.5 Cr 2 O 4 chromite spinel prepared using sol-gel method were investigated. The TGA and DSC analyses were used to study the spinel phase formation and the weight loss during the synthesis process for the sample. The XRD and TEM characterizations confirmed the development of the cubic spinel structure. From the FTIR spectrum, the characteristics vibrational modes corresponding to the spinel structure were observed. From the room temperature UV–Vis optical absorbance, the synthesized chromite sample shows a significantly lower direct band gap ( E gd = 1.90 eV) and has an appropriate absorption rate in the visible light region. Magnetization ( M - T curve) shows a second order magnetic phase transition from the ferrimagnetic (FiM) behavior to the paramagnetic (PM) behavior at the Curie temperature T C = 40 K. By comparing our results to those previously found for the NiFe 2 O 4 spinel, we can conclude that the substitution of Mn for NiFe 2 O 4 increases its magnetization and decreases its coercivity. The magnetocaloric performances achieved for Ni 0.5 Mn 0.5 Cr 2 O 4 sample are quite comparable to several literature values found for other chromite spinels.