The Magnetic Properties of Perpendicular FePt Thick Films and the Written Patterns for a T-ray Source Undulator

Sungwon Choi, Sun-il Han, Kungwon Rhie, Pyungwoo Jang, Byungcheol Lee, Hee-Jun Chung

The feasibility of a micro-undulator using several 2.6 μm thick FePt films and perpendicular recording techniques was confirmed in a previous study. However, samples with this thickness can not be recorded magnetically, because of the large coercive force. A writable low coercive force with a high enough stray field of 3 kOe for a facing undulator was achieved with a 20 μm thick FePt film. The coercivity of the FePt film was reduced by increasing the film’s thickness and by changing the Fe and the Pt compositions. The written magnetization was confirmed with Bitter patterns and Hall effect measurements. The stray magnetic field measured with a Hall sensor after perpendicular magnetic recording was confirmed from simulations and matched the exprimental value very well. This thick perpendicular magnetic film with magnetic recording can be applied to spintronics devices as well as micro magnet for a THz source.

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