Influence of sputter gas and sputter pressure on the structure and magnetic properties of Co–Pt–Cr thin films (abstract)

Abstract

The magnetic properties of high density recording media have been shown to be very sensitive to the film microstructure. We have investigated the influences of different sputter gases (Ar, Xe, Kr) and different sputter pressures (3 to 24 mTorr) on the microstructures and magnetic properties of CoPtCr/Cr thin films. The magnetic properties of the films (coercive field, Hc, coercive squareness, S*, and remanant moment, Mr) were determined using a vibrating sample magnetometer. The microstructures were examined by transmission electron microscopy and x-ray diffraction. For all three gases studied the microstructures and properties of the CoPtCr films were found to change with sputter pressure in similar manners. Films deposited at the lowest pressure consisted of well connected, equiaxed grains. With only a slight increase in pressure, the grains formed chains separated by small gaps. As the gas pressure increased further, the chains became better defined and the gaps between them widened. The coercive squareness and coercive field correlate with the film microstructures. S* decreased with increasing sputter gas pressure, and Hc first increased and then decreased. For all three sputter gases, Hc reached a maximum around 12 mTorr. Likewise, S* decreased quite slowly with increasing pressure up to 12 mTorr and then exhibited a sharp drop between 12 and 18 mTorr. From these results it appears that the sputter pressure, rather than the mass of the sputter gas, is most important for the microstructural development of the film. Likewise, the values of S* were found to be independent of the sputter gas. However, in spite of the similar microstructures, films deposited with Ar had higher values of Hc than films deposited with Xe or Kr, for all sputter pressures examined. The role of the sputter gas mass will be discussed.