RELATION BETWEEN MICROSTRUCTURE OF GRAIN-BOUNDARY AND THE INTERGRANULAR EXCHANGE IN COCRTA THIN-FILM FOR LONGITUDINAL RECORDING MEDIA

In CoCrTa films, the relationship between the microstructure of grain boundaries and degree of intergranular exchange coupling was investiga ted. The degree of intergranular exchange coupling decreases as Ta con tent increases. By TEM observation, it was revealed that the boundary phase, which appears to be amorphous, surrounds the grains. The width of this boundary phase tends to become thicker as Ta content increases From the result of an EDS analysis, the Cr content at the grain bound aries is higher than that in the grains. The boundary phase may be non -magnetic due to its high concentration of Cr. On the other hand, in t his experiment, no boundary phase was observed in CoNiCr and CoCrPt fi lms which have the higher degree of intergranular exchange coupling th an CoCrTa films. Therefore, the change in the boundary phase may be ef fective In reducing the degree of intergranular exchange coupling.