Formation of Ordered FePt(001) Texture With Reduced Diffusion Length

Abstract

Samples with glass/CrRu(90 nm)/Pt(2 nm)/FePt(20 nm) film structure were sequentially planetary-sputtered at an in situ heating temperature of 350degC to investigate the effect of sputtering rate on the ordering of L1 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> -FePt (001) films. The degree of chemical ordering was enhanced by lowering the sputtering rate of the FePt layer. The slow sputtering process also promoted the formation of the (001) preferred orientation by improving epitaxial growth, because the thickness of the Fe and Pt layers in each revolution become smaller as the sputtering rate was reduced. Therefore, the diffusion lengths of the Fe and Pt atoms required for migration into the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</i> 1 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> lattice sites became shorter. The sputter parameters can be optimized to form ordered FePt (001) films with a high magnetic squareness ratio ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.8)</i> and large coercivity at 300degC, which is 50degC lower than in previous reports. The results herein provide useful information on the fabrication of FePt films with perpendicular anisotropy at low temperatures in media use.