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.

Variation 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 as PowerPoint slide