Incoherent Switching Amount Analysis of Exchange Spring Media by Using Initial Minor Loop Slope Measurement

We describe a newly developed initial minor loop slope (IMLS) experimental method capable of measuring reversal switching in exchange spring perpendicular media. The slope peak height is centered near the medium's coercivity H
_c
. The magnitude of the peak signal is correlated with the soft top (cap) layer's moment, M
_s
t, and the exchange coupling strength between the cap and hard magnetic oxide layers. The peak position was correlated to the media Hc for media that is thermally stable and migrates to smaller fields in less stable media. The IMLS results are compared with both remanent angular dependence coercivity, H
_cr
, measurements and micro-magnetic simulations. This technique provides a simple method of characterizing incoherent switching behavior in different types of exchange spring media.