Tailoring out-of-plane magnetic properties of pulsed laser deposited FePt thin films by changing laser energy fluence

•Laser energy fluence (LEF) effect on composition, microstructure and magnetism.•Enhancing out-of-plane magnetic properties by tailoring LEF on target surface.•Higher LEF results in more energetic plasma species causing vacancy defects.•Formation of vacancy defect in FePt thin films leads to improved magnetic properties.•Best out-of-plane magnetic properties are achieved with medium LEF. Magnetic properties of pulsed laser deposited (PLD) FePt thin films are investigated at three different laser energy fluences of 51, 136 and 182J/cm2. Deposition at lower laser energy fluence (51J/cm2) yields softer out-of-plane coercivity (≤0.4kG), whereas deposition at higher laser energy fluence (136 and 182J/cm2) results in harder out-of-plane coercivity (≥5.0kG). The improved coercivity is found to be attributed to the formation of vacancy defects in thin films, which is indicated by stress change from tensile to compressive form with increasing laser energy fluence. Maximum out-of-plane saturated magnetization of 615emu/cm3 and remanent squareness ratio of 0.88 are achieved for 16nm thick FePt thin films deposited at moderate laser energy fluence of 136J/cm2, making them suitable for high density perpendicular data storage applications.