For heat assisted magnetic recording (HAMR) media development, measurement of erasure
temperature (Te) is interesting and important for practical HAMR testing and applications. Here,
we present an investigation on Te measurements of L10 ordered FePt granular HAMR media made
using a Laser Heating (LH) method on a home-built HAMR write test system versus that from a
bulk heating approach. The HAMR write test system provides HAMR writing, micro-MOKE (magneto-
optical Kerr effect) signal detection, and MOKE imaging functions at the same testing spot in
one single system. Magnetic force microscopy (MFM) and magnetic Kerr microscopy observations
of the scanning laser induced degradation/erasure/demagnetization of the pre-recorded magnetic
patterns on disk media (over a wide area of a few hundreds of lm2) show that the magnetic (MFM
and Kerr signal) amplitude of the pre-recorded magnetic patterns decreases slowly with increasing
laser power (Pw) (/temperature rise) for Pw 66 mW and then drops sharply to nearly zero for
Pw 72 mW (the laser power corresponding to complete thermal erasure when the media temperature
is Te). It was further found that this trend of magnetic amplitude reduction with
increased Pw is similar to that from magnetic amplitude decrease of pre-recorded magnetic patterns
with increased bulk heating temperature. The temperature for complete erasure at laser power,
Pw¼72 mW for the LH method, corresponds therefore to 650K ( Te) for the bulk heating
methods. Besides fast measurement, LH (as a comparable and viable approach for erasure measurement)
is dynamic, localized, and has time scales closer to practical HAMR situation.
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Copyright (2015) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in J. Appl. Phys. 117, 17D117 (2015) and may be found at http://dx.doi.org/10.1063/1.4914362.