The magnetic anisotropy of Co{sub}(100-x)Cr{sub}14Pt{sub}8B{sub}x longitudinal thin film recording media sputtered onto Al/NiP substrates has been determined as a function of boron concentration (x=4at% to x=16at%) using high field (～4.5T) ferromagnetic resonance (FMR) [1] and the Miyajima technique [2]. The variation of coercivity with field exposure time has also been measured over two different time regimes allowing the median reversal field, in the absence of thermal activation, H{sub}0, to be determined using Sharrock's equation [3, 4]. The first time regime was set by the field response time of a large electromagnet capable of providing fields up to 2T. The minimum field exposure time for those measurements was 5secs. Mounting the medium on a spinstand and using the write element of a magnetic recording head as a field source and GMR reader as a sensor allowed access to sub-microsecond time scales.
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