First-principles calculations for the structural and magnetic properties of ordered NiFe(001) thin films with and without a Ta overlayer

The first-principles calculations within the local density approximation us ing the full potential linearized augmented plane wave (FLAPW) method were performed to investigate the structural and magnetic properties of the Ta/N iFe interface for both clean NixFe1-x (001) thin films and with a Ta overla yer. To study the composition dependence, we adopted x = 0.5 (L1(0) structu re with either Fe or Ni layers on the surface) and 0.75 (L1(2) structure wi th mixed Fe-Ni layers or with Ni on the surface). The equilibrium overlayer /substrate distance and the preferred site position of Ta were obtained by structural optimization employing atomic-force calculations and total energ y comparisons for several possible adsorption sites of Ta. By comparing wit h results for the clean surface of five-layer NixFe1-x (001) films, we foun d that Ta has a significant detrimental effect on the magnetic properties o f NiFe with its induced magnetic moment coupled ferro- or antiferro-magneti cally with the substrate depending sensitively on the surface layer. (C) 20 00 American Institute of Physics. [S0021-8979(00)73908-9].