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ABSTRACT
An optical method is proposed to real-time monitor the order transformation of FePt thin films. By measuring the surface reflection amplitude, onset temperature can be determined correctly. In a heating process, order transformation drastically increases the surface roughness due to recrystallization and grain growth, resulting in rapid drop of surface reflectivity. By tracking this drop, the kinetic ordering temperature can be determined. Experimentally measured kinetic ordering temperature for Fe50.4Pt49.6, Fe46.6Pt53.4, and Fe52.7Pt47.3 thin films of 60 nm in thickness are 396°C, 437°C, and 368°C, respectively. They are in good agreement with the published DSC data.
Nomenclature
| Hc | = | Magnetic coercivity |
| Ku | = | Magnetocrystalline anisotropy |
| M2T | = | Magnetization at external magnetic field of 2 tesla |
| Mr2T | = | Remanence of the sample after magnetizing by magnetic field of 2 tesla |
| S | = | Order parameter of FePt alloy |
Disclosure statement
No potential conflict of interest was reported by the authors.