Evaluation of the next generation magnetic recording media (FePt) by in-plane X-ray diffraction
As a next generation, ultrahigh density magnetic recording media, granular thin films in which metal microparticles are dispersed have been a focus of attention. Among them, the irregular phase (tetragonal crystal) of FePt has a particularly high magnetic anisotropy and has also good corrosion and oxidation resistances, so it is expected that it will be applied to actual devices. However, the regular phase (cubic crystal) is created at the same time, depending on the film-forming conditions. For this reason, a technique to distinguish these crystalline phases at the nanoparticle and thin film level is required.
Using the in-plane X-ray diffraction method, in which X-rays are irradiated on the surface of a thin film sample at a glazing angle to study the regular structure (crystal structure) in the in-plane direction, it is possible to identify the crystal phase for even an ultra thin film only a few nm thickness. It is also possible to analyze the sample in the depth direction by changing the incident angle of X-rays entering the sample surface.
The
figure above shows profiles of in-plane measurement, taken with Rigaku's SmartLab multipurpose
diffractometer, of samples where a 15 nm thick FePt film is formed on a glass
substrate on which a silver (Ag) layer is deposited in four different
thicknesses. As the Ag film thickness increases, crystallization of the FePt
regular phase advances. Signals from the Ag layer, which is only 1 nm
thickness, are also detected.
The figure to the right shows the results of a diffraction experiment where the incident angle is changed on a sample that is a 1 nm thick Ag layer on the glass substrate. When the incident angle is shallow, the signals become relatively strong, suggesting that the silver (Ag) exists in the shallow surface of the sample.
References:
- Z. L. Zhao et al, Appl. Phys. Lett., 83, 2196 (2003).
- Z. L. Zhao et al, J. Appl. Phys. 95, 7154 (2004).
Tags: SmartLab, , thin film, orientation, composition