SATURATION-MOMENT VARIATION AND CR SEGREGATION IN COCR-SPUTTERED FILMS

We have investigated saturation magnetization (Ms) variation and Cr segregation in CoCr rf-sputtered films. Using a special substrate- temperature monitoring system, which provides in situ measurements, the relationships of Ms to substrate temperature (Tsub) and Tsub to sputtering parameters have been investigated for films sputtered from both alloy and mosaic targets. Ms was found to increase as Tsub decreased. Little difference was found between films sputtered from the two different types of targets. A theoretical model has been developed for calculation of equilibrium Cr segregation on grain boundaries. The composition of atomic planes near a grain boundary, depletion of the crystal core, and Ms of the crystals can be calculated as a function of temperature. Although the predicted amount of Cr segregation is in agreement with experimental measurements in the literature, the predicted variation of Ms with temperature is only a small fraction of what is seen experimentally. It is concluded that mechanisms other than Cr segregation must be found to provide the explanation for the variation of Ms in CoCr films.