Lattice strain induced magnetism in substituted nanocrystalline cobalt ferrite

•Increase of lattice parameter and strain due to Sr substitution in cobalt ferrite.•Magnetism due to lattice strain in nonmagnetic (Sr) substituted cobalt ferrite.•Structural and magnetic phase diagram for nonmagnetic (Sr) substituted cobalt ferrite.•Magnetocrystalline anisotropy constant anomaly at 1% Sr substitution in cobalt ferrite.

Strontium (Sr) substituted cobalt ferrite i.e. Co1−xSrxFe2O4 (x  =0.00, 0.01, 0.015, 0.02, 0.05, 0.1) have been synthesized by the citric acid modified sol–gel method. Crystal structure and phase purity have been studied by the X-ray powder diffraction technique. The Rietveld refinement of XRD pattern using the space group Fd3¯m shows monotonically increasing of lattice parameter with the increase in Sr concentration. Magnetic hysteresis loops measurement has been carried out at room temperature using a vibrating sample magnetometer (VSM) over a field range of ±1.5 T. Magnetocrystalline anisotropy constant were calculated by employing the Law of Approach (LA) to the saturation. It is observed that magnetocrystalline anisotropy has anomaly for x=0.01 (Co0.99Sr0.01Fe2O4) sample. Strain mediated modification of magnetic properties in Sr substituted cobalt ferrite has been observed. The saturation magnetization for doping concentration i.e. x=0.01 abruptly increase while for x>0.01 decreases with the increase in Sr concentration. A correlation between lattice strain and magnetic behavior in non-magnetic Sr- substituted nano-crystalline cobalt ferrite has been reported.

Graphical abstractVariation of coercive field and saturation magnetization with Sr-concentration. Variation of lattice strain has been replotted for better presentation. The shaded regions are strain dominated magnetic property modified region.Figure optionsDownload full-size imageDownload as PowerPoint slide