Surface magnetic hysteresis, measured by Polar M.O. Kerr effect on RF and Magnetron sputtered CoCr (81/19 at%) films in the range 20 - 4000 nm is compared with volume hysteresis measured by VSM, both with external field perpendicular to the surface. The surface coercivity H cs was found to decrease below the volume coercivity at a critical thickness of 125 nm for RF films  and at about 1100 and 800 nm for centre and off-centre Magnetron samples respectively. The slope of the Kerr loop at qk = 0 increased slightly again deviating from the VSM slope at a film thickness of about 100, 800 and 500 nm for RF, centre and off-centre Magnetron CoCr samples respectively. These results are consistent with formation of small spikes from the surface for films thicker than a critical value. Order of magnitude calculations do not oppose the formation of such small reversed domains and the higher critical thickness for Magnetron samples is also in qualitative agreement with these calculations, due to a higher perpendicular anisotropy by a factor 2 for these films. If spike domains do exist in CoCr the reversal mechanism is most likely one in which the reversed domains grow at the expense of the main domains.
|Number of pages||3|
|Journal||IEEE transactions on magnetics|
|Publication status||Published - 1987|
|Event||International Conference on Magnetic Recording Media, MRM 1986 - Sala Aurea Parma, Parma, Italy|
Duration: 2 Sep 1986 → 5 Sep 1986
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