First-principles and Monte Carlo studies on the magnetic stability of half-metallic zinc-blende CaC and similar compounds

Using the first-principles calculation based on density functional theory and Monte Carlo simulation within the Heisenberg Hamiltonian, we have investigated the magnetic stability at finite pressure and temperature of CaC and some other selected hypothetical II^A-IV^A compounds with the zinc-blende crystal structure. The results from simulated external pressure and temperature test indicate that the magnetic stability is dependent on the variation in atomic number of anion or cation element. Additionally, the origin of sp magnetism is mentioned briefly in this work and the dependence of Curie temperature on the volume is also discussed. First-principles computational charge-injection test show that the magnetization of these sp compounds originates in the spin polarization of the p shell of anions. For CaC, the exchange parameter J₁ of the Heisenberg Hamiltonian depends strongly on the lattice constant, while the J₂ and J₃ are weakly dependent on the lattice constant. Moreover, discussion of volume-conserving deformations for CaC further demonstrates the stability of ferromagnetism and half metallicity for the compounds.