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Effects of DC Bias on the Thermal Stability of DC In-Line Sputtered CoCrTa/Cr Thin Film Media

Published online by Cambridge University Press:  10 February 2011

J. P. Wang ,
L. P. Tan ,
T. Y. F. Liew ,
T. S. Low ,
H. L. Wong  and
Y. K. Lee
J. P. Wang
Affiliation:
Data Storage Institute, National University of Singapore, 10 Kent Ridge Crescent, Singapore119260
L. P. Tan
Affiliation:
Data Storage Institute, National University of Singapore, 10 Kent Ridge Crescent, Singapore119260
T. Y. F. Liew
Affiliation:
Data Storage Institute, National University of Singapore, 10 Kent Ridge Crescent, Singapore119260
T. S. Low
Affiliation:
Data Storage Institute, National University of Singapore, 10 Kent Ridge Crescent, Singapore119260
H. L. Wong
Affiliation:
StorMedia International Ltd (Singapore Branch), 9 Tuas Avenue 5, Singapore639335
Y. K. Lee
Affiliation:
StorMedia International Ltd (Singapore Branch), 9 Tuas Avenue 5, Singapore639335
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Abstract

The effects of DC bias on the thermal stability and magnetic anisotropy of CoCrTa/Cr thin film media fabricated by using a DC in-line sputtering machine is presented in this paper. In sputtering, a negative DC bias voltage, varying from 0 to 400 V, was applied for the CoCrTa layer. The coercivity was observed to increase almost linearly from 1800 to 2300 Oe for negative bias voltage from 0 to 400V. The thermal stability of these media was studied by measuring the time decay of remanent magnetization under various reverse magnetic fields. The maximum value of the magnetic viscosity coefficient, which happens around remanent coercivity of each samples, decreases with increasing substrate bias voltage. This implies an improvement in the thermal stability of the CoCrTa/Cr thin film media. The magnetic anisotropy constants were measured using both a torque magnetometer and a vibrating sample magnetometer. The magnetic anisotropy measured using torque magnetometer decreases, while that measured using the method of the law of approach to saturation was found to be almost constant, with increasing bias voltage. The activation volumes decreased with increasing bias voltage. The magnetic hardness coefficient determined using the law of approach to saturation, indicating the number of in-depth defects in the CoCrTa layer, increased with increasing bias voltage. The internal stress in these films measured using X-ray diffractometer also supported the existence of in-depth defects. The pinning of the rotation of magnetization by these defects in the magnetic grains maybe responsible for the improvement of thermal stability.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 517: Symposium F – Wide Bandgap Semiconductors for High Power, High Frequency , January 1998 , 273
Copyright
Copyright © Materials Research Society 1998

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