The magnetism of FeCoxB alloys: First principle calculations

Calculations of magnetism are made on transition metal monoboride of FeCo_xB, with the scale 0⩽x⩽1. In this paper, we calculate the ferromagnetic variation of transition metal monoboride by the method of virtual crystal approximation (VCA), based on density-functional theory (DFT) with generalized gradient approximation (GGA). The variations of ferromagnetism of FeCo_xB alloys by the first-principle spin-polarized calculations are in agreement with experimental results, the prediction of the Stoner model and the Korringa-Kohn-Rostoker (KKR) method with coherent potential approximation (CPA). The spontaneous magnetization decreases with increasing x and vanishes at around x=0.85. This complies with earlier findings. The instability at around x=0.8 is elucidated by electron filling of the Fe 3d orbital both from valence and interstitial electrons.