Structural and magnetic effects of Mn addition on CoB amorphous alloy by first principle simulation

Abstract

First-principle molecular dynamics is employed to study the geometrical structure, electronic structure, and magnetic properties of Co80-xMnxB20 (x = 0, 2, 4, 6, 8, 10, 12 at.%) amorphous alloys. Results demonstrate that Mn atom locates at substituted positions of Co atoms, and cage structure with Mn as a center is mainly a twisted Icosahedral structure. Mn or Co atoms tend to lose electrons, and B atoms tend to gain electrons. The addition of Mn atoms increases the splitting of p band of B atoms. Variation of magnetic moment increases and then decreases with the increase of Mn content. Simulation results are in good agreement with experiments. Magnetic moment of Mn atoms in amorphous alloy exhibits ferromagnetic arrangement when x > 6 at.%. However, when x > 6 at.%, some antiferromagnetic arranged Mn atoms appear, and there is a competition between ferromagnetism and antiferromagnetism in the alloy, which makes magnetic moment of the amorphous alloy gradually decrease.