An ab initio study of the magnetocrystalline anisotropy and magnetoelastic coupling of half-metallic CrO₂

First-principles density functional calculations of the total energy, magnetic moments and magnetocrystalline anisotropy energy (MAE) of CrO ₂ as a function of both volume and uniaxial strain along the c-axis have been performed. The highly accurate all-electron full-potential linearized augmented plane wave method and the generalized gradient approximation to the exchange-correlation potential are used. The calculated structural properties (lattice constants and unit cell volume) are in excellent agreement with experiments (with 0.5%). The calculated bulk and Young's modulii are 2.56 and 2.02Mbar, respectively. The calculated MAE increases almost linearly with the uniaxial strain and remains positive in the strain range of -4-4%. Thus, the calculations predict that the easy magnetization axis is along the c-axis, in agreement with experiments. However, the calculated anisotropy constant is about six times larger than the measured value. The calculated magnetoelastic coupling constant is 1.2×10⁷erg/cm³ and the magnetostriction coefficient λ₀₀₁ is -2.59×10 ^-5.