Manipulation of the magnetization by external energies other than magneticfield, such as spin-polarized current1-4, electric voltage5,6 and circularlypolarized light7-11 gives a paradigm shift in magnetic nanodevices.Magnetization control of ferromagnetic materials only by circularly polarizedlight has received increasing attention both as a fundamental probe of theinteractions of light and magnetism but also for future high-density magneticrecording technologies. Here we show that for granular FePt films, designed forultrahigh-density recording, the optical magnetic switching by circularlypolarized light is an accumulative effect from multiple optical pulses. Wefurther show that deterministic switching of high anisotropy materials by thecombination of circularly polarized light and modest external magnetic fields,thus revealing a pathway towards technological implementation.
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