Study of magnetic field determined from vanishing rotational hysteresis loss in CoCrPtB perpendicular thin film media

The magnetic field determined from vanishing rotational hysteresis loss of CoCrPtB perpendicular thin film media was experimentally investigated. It was clarified that (1) in Co ₇₂Cr ₁₆Pt ₈B ₄ media with d _mag of less than 200 nm and Co ₆₄Cr ₂₄Pt ₈B ₄ media with d _mag of less than 100 nm, a homogeneous structure was realized, except for the existence of an initial growth region. (2) For both media, the perpendicular rotational hysteresis loss, W _r, the maximum field of W _r, H _p, and the field where W _r=0, H _Wr=0, increased with an increase in d _mag. (3) For both media, H _Wr=0/H _k ^grain increased with an increase in d _mag and saturated at a magnitude of about 1. (4) For the medium with thin magnetic film thickness, at applied field of H _Wr=0 <H<H _k ^grain, a multidomain state was realized in the torque measurement in spite of no observation of loss of rotational hysteresis. This is considered to be due to the existence of thermal agitation between the multidomains.