Irradiation of FePd[sic FePt] and FePd films for perpendicular magnetic recording

Summary form only given. FePt and FePd films are presently attracting a wide interest because in the L1/sub 0/ tetragonal chemically ordered phase they exhibit a very high magnetic anisotropy. These properties make them attractive candidates as high-density magnetic recording media. However, the high growth temperature needed for ordering (∼ 400°C) is not compatible with manufacturing techniques. In this study, we show that if a high degree of short range order (SRO) is present in FePt and FePd disordered films, a high value of the long range order parameter S can be obtained by using post growth ion irradiation at very low processing temperatures (T/sub 1rr/ < 200°C). FePd and FePt [001] films were deposited monolayer by monolayer by MBE on MgO[001] at room temperature. In such films the degree of long range order (LRO) is very weak (S∼0.1). However as indicated by EXAFS measurements the degree of SRO is high due the directional order induced by the layer by layer growth. We used He/sup +/ ions at low fluence and temperatures of irradiation T/sub 1rr/ ranging from 20-300°C. In such conditions the ions move the atoms on a few interatomic distances and allow to modify in a controlled way the SRO. We demonstrate that high long range chemical ordering and high perpendicular anisotropy can be obtained at very low irradiation temperatures (< 200°C). This could have a great impact on current race toward high magnetic recording density media.