Effects of bias-sputtering on magnetron-sputtered magneto-optical recording media

Effects of substrate bias on the magnetic properties and microstructure of both RF-magnetron- and DC-magnetron-sputtered magnetooptical recording thin films of TbCo are investigated. It is shown that as an applied RF substrate bias voltage (V_b ) becomes more negative, argon entrapment in the TbCo films increases precipitously and the deposition rate decreases. Applying V_b more negative than -30 V (at a cathode voltage of -0.5 kV) results in the formation of voids and a columnar microstructure in magnetron-sputtered films. The diffraction patterns of these amorphous films reveal traces of microcrystallites a few nanometers in size. In addition to the dominant perpendicular anisotropy, evidence of in-plane magnetization is detected. In contrast to what has been found for RF diode sputtering, substrate bias thus adversely affects the properties of magnetron-sputtered films