Thickness dependent magnetic properties of (111)-oriented Co_0.8Fe_2.2O₄ thin film grown by pulsed laser deposition

The perfect (111)-oriented Co_0.8Fe_2.2O₄ thin films are grown on Pt(111)/Si substrate using pulsed laser deposition technique at substrate temperature of 600 °C and laser pulse rate of 5 and 10 Hz. The Fe K-edge X-ray absorption near edge structure analyses revealed that Fe in Co_0.8Fe_2.2O₄ films deposited at both 5 and 10 Hz exists in Fe^{3 +} state leading to the actual composition of Co_0.8Fe_2.2O_{4 +δ}. In order to study the effect of film thickness on the magnetic properties, the film thickness was increased by increase in the pulse rate as well as the time of deposition during pulsed laser deposition process. It was found that by increase of the film thickness, the saturation magnetization and squareness will be generally increased. In the films with same thickness, those which deposited at higher pulse rate have a higher coercivity. In the films deposited at same pulse rate (10 Hz) and different time of deposition, the saturation magnetization, coercivity, and squareness were increased by increasing the thickness, but the coercivity will be decreased with further increasing the thickness due to the relaxation of residual stresses.