Coercivity, microstructure and magnetization reversal mechanism in TiNi-doped L10 FePt thin films

• The small and uniform size of ordered domain, lower coercivity and weak intergranular exchange coupling interaction are observed.
• The TiNi doping separates FePt grains and provides the nucleation center of reversed domain.
• The magnetization reversal mechanism is the combination nucleation and pinning of domain walls.
• The coercivity reduction may be caused by the decrease of anisotropy constant and nucleation field of the reversed domain.

Controlling coercivity and understanding how it is affected by the microstructure are of essential importance for practical application of FePt thin films as a recording media. In this study, the small size of ordered domain, lower coercivity and weak intergranular exchange coupling interaction in TiNi-doped L10 FePt thin films are obtained. The TiNi additions maybe diffuse out of the FePt lattice into FePt grain boundaries, which separate FePt grains. The doping in grain boundary provides the nucleation center of reversed domain, which leads both nucleation-type and pinning-type mechanism to coexist in magnetization reversal processes for TiNi-doped FePt thin films. The decrease of anisotropy constant and nucleation field of reversed domain provides an explanation for the coercivity reduction of FePt thin films after TiNi doping.