Electronic Resource
[S.l.]
:
American Institute of Physics (AIP)
Journal of Applied Physics
70 (1991), S. 5478-5489
ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
The size and shape of the magnetic inhomogeneities in various particulate recording tapes have been studied using neutron depolarization (ND). The tapes are in the remanent magnetic state either during the dc-demagnetization reversal process or after bulk erasure, ac erasure, or thermal annealing. The magnetic correlation length ζ measured along the direction perpendicular to the plane of the tape (Z direction) is at most twice the particle diameter in the dc-(de)magnetized tapes, indicating the existence of clusters and switched volumes containing only a few particles along Z. The switched volumes are the magnetic inhomogeneities in the demagnetized state. A cluster is a group of particles in which the mean particle orientation or density differs from the mean particle orientation and density within the tape. The size along Z of the switched volumes after bulk or ac erasure is slightly smaller than that of switched volumes after dc demagnetization. After thermal annealing, the magnetic correlation length is smallest and corresponds either to magnetically uncorrelated particles or to weak negative magnetic correlations along Z. The latter would indicate a weak antiparallel orientation of the magnetization in neighboring particles in the Z direction. From ND experiments in which the direction of the neutron beam is varied in the YZ plane (length direction tape along Y), it follows that the switched volumes and clusters are elongated along Y, with aspect ratios generally larger than ten. The clusters in Philips CrO2 video tapes are oriented mainly in the YZ plane. The switched volumes in ac- or bulk-erased TDK Co-modified γ-Fe2O3 video tapes closely resemble the particle volume.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.350205
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