Improvement in hard magnetic properties of FePt films by N addition.

The structure and magnetic properties of (Fe[sub 56]Pt[sub 44])[sub 100-x]N[sub x] alloy films with x=0–15 at. % prepared by rf magnetron sputtering were investigated. Compared to an Fe[sub 56]Pt[sub 44] binary film, (Fe[sub 56]Pt[sub 44])[sub 100-x]N[sub x] alloy films showed great enhancement in hard magnetic properties. A coercivity H[sub c] of 1027 kA/m, a remanence M[sub r] of 1.24 T, and a maximum energy product (BH)[sub max] of 260 kJ/m3 were obtained for an (Fe[sub 56]Pt[sub 44])[sub 93]N[sub 7] film annealed at 600 °C for 10 min, whereas the Fe[sub 56]Pt[sub 44] film annealed at the same conditions gave H[sub c]=682 kA/m, M[sub r]=0.87 T, and (BH)[sub max]=132 kJ/m[sup 3]. Structural analysis revealed that N addition influenced the phase structure and microstructure of FePt films. N atoms incorporated in the disordered FePt phase in as-deposited films, they released rapidly out of the FePt phase by vacuum annealing. It is suggested that the rapid release of N atoms from the FePt phase promotes the transformation to the ordered phase, results in a higher coercivity of the film. The high remanence of the (Fe[sub 56]Pt[sub 44])[sub 93]N[sub 7] film is attributed to enhanced exchange coupling of the soft iron nitride phase and the hard FePt phase. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]