Volume dependent magnetism in zinc-blende MnX (X=N,P,As,Sb,Bi) compounds

Half-metallic ferromagnets are promising candidates for use in spintronic devices. In order to investigate the complex magnetism of such systems, we have studied the magnetic interactions in zinc-blende MnX (X=N,P,As,Bi,Sb) systems as a function of volume by ab initio density functional calculations. The calculated Heisenberg pair-exchange parameters show a strong volume dependence resulting in the transition from a metallic to a half-metallic behavior for certain systems. As a result, in MnAs, the calculated Curie temperatures, obtained from Monte Carlo simulations using ab initio exchange parameters and a classical Heisenberg Hamiltonian, increase with an increase in volume. Calculations of self-consistent noncollinear spin configurations indicate that spins deviate strongly from collinear ordering for low volumes whereas they align in a collinear ferromagnetic fashion for high volumes. (C) 2008 American Institute of Physics.