EFFECTS OF SUBSTRATE TEMPERATURE ON INTERGRANULAR INTERACTIONS AND RECORDING PERFORMANCE OF CoCrTa/Cr THIN FILM MEDIA

Abstract

Abstracts---The magnetic properties, intergranular interactions, and recording noise of longitudinal CoCrTa/Cr thin film media have been investigated as a function of substrate temperature. It was found that the in-plane remanent coercivity was increased from 580 Oe for deposition at 25 QC to 1480 Oe for deposition at 220 QC. It was also found that preheating substrates to 270 QC reduced the medium noise power as much as 9.5 dB. Measurement of SM curves indicated that the dominant magnetic interactions in CoCrTa/Cr films was shifted from strong positive interactions, possibly intergranular exchange, to weaker negative magnetostatic interactions as the deposition temperature was increased. This reduction of magnetic coupling is believed to cause the decrease in the recording noise. In addition, the relation between recording noise and remanent coercivity squareness has been derived and their relationship was discussed on the basis of experimental results.

COMPARISONS OF MEASURED AND CALCULATED ANGULAR DEPENDENCE OF COERCIVITY OF LONGITUDINAL CoCr/Cr THIN FILMS

“…The measurements of the angular dependence of apparent coercivity for CoCr/Cr films reported by Lu et al [2] are normalized by the zero-degree coercivity, H co ' and are shown as specific points in Fig. 2.…”

“…The demagnetization factor is assumed to be 47t when the applied field is directed normal to the thin film plane and zero when the field is directed in the plane of the film. The magnitude of the demagnetization field, H d , is calculated by using Hd = -4 7t sin ~ , (2) where ~ is the out-of -plane angle of the magnetization vector, e.g., ~ = El-<I> for the vertical-plane easy axis distribution. The magnitude of Hd is corrected by the component of ~x.…”

“…The purpose of this paper is to report on investigations of the micromagnetization reversals possible in longitudinal CoCr/Cr thin films by comparing calculations of the angular dependence of apparent coercivity with measurements reported by Lu et al [2] taking into account the corrections for demagnetization fields in the direction of applied fixed-direction external field and the effects of the distribution of easy axes. This paper does not take into account the interparticle interactions and does not address the full correctons for demagnetization fields in thin films as was done experimentally by Bernards and Cramer [8] for measuring the true coercivity.…”

“…The angular dependences of the apparent coercivity of CoCr/Cr thin films have been measured and the micromagnetization reversal processes have been discussed without corrections of demagnetization fields [2]. The effects of demagnetization fields must be taken into account when comparing magnetization measurements with calculations in order to determine the most likely mechanism of magnetization reversal [3][4][5][6].…”

“…for the thin film. Calculations are compared with the measurements for CoCr/Cr thin films by Lu et al [2]. It is shown that the curves of the angular dependence of apparent coercivity for 4000A CoCr/Cr thick films with or without 3000A Cr underlayer can be explained by the curling rotation process, and that a 3000A thick Cr underlayer induces a change of the micromagnetization reversal for 350A CoCr thin films from fanning to curling and an increase of the in-plane component of the easy axis distributions.…”