Influences of sputtering gas pressure on microtexture and crystallographic characteristics of Ba-ferrite thin films for high density recording media

Abstract

Ba-ferrite films with small c-axis dispersion angle Δθ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">50</inf> are suitable for ultrahigh density recording media. The dependences of partial oxygen gas pressure P <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">O2</inf> and total discharge gas pressure P <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Total</inf> on the characteristics of Ba-ferrite films were clarified. It was found that there were three regions, where films were composed of single layer of spinel type ferrite(P <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">O2</inf> ≤0.002mTorr), mixed layer of spinel and magnetoplumbite type ferrites ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.003 \leq P_{O2} \leq 0.2</tex> mTorr) and single layer of magnetoplumbite type ferrite (P <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">O2</inf> >0.3 mTorr). In the range of P <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">02</inf> between 0.005 and 0.2 mTorr, spinel-like ferrite layer plays very important role as an underlayer to decrease the Δθ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">50</inf> of the Ba-ferrite layer. Films deposited at relatively low P <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">O2</inf> and P <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Total</inf> exhibit very smooth surface and Δθ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">50</inf> as small as <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2.5\sim3.5\deg</tex> .