Underlayer and substrate effects in RF-magnetron sputtered barium ferrite thin film media

The effect of employing various sputtered underlayers and commercially available substrates in order to optimize the characteristics of barium ferrite (BaM) thin films for magnetic recording media have been studied. Our results show that the choice of underlayer or substrate controls the resultant surface morphology and magnetic properties of the BaM film. In particular, it was found that barium ferrite thin films with high coercivity, good squareness, low switching field distribution (> 5000 Oe, 0.92, and 0.58, respectively) and possessing a c-axis in-plane orientation texture were achieved when deposited on an amorphous sputtered underlayer of Al2O3. In addition, the use of an Al2O3 underlayer results in equiaxial barium ferrite grains which may allow a favorable reduction in intergranular interaction as evidenced by the characteristic Delta M curves.