First principles study of structural, magnetic and electronic properties of half-metallic CrO<Subscript>2</Subscript> under pressure

A first-principles tight-binding linear muffin tin orbital (TB-LMTO) method within the local-density approximation is used to calculate the total energy, lattice parameter, bulk modulus, magnetic moment, density of states and energy band structures of half-metallic CrO<Subscript>2</Subscript> at ambient as well as at high pressure. The magnetic and structural stabilities are determined from the total energy calculations. From the present study we predict a magnetic transition from ferromagnetic (FM) state to a non-magnetic (NM) state at 65 GPa, which is of second order in nature. We also observe from our calculations that CrO<Subscript>2</Subscript> is more stable in tetragonal phase (rutile-type) at ambient conditions and undergoes a transition to an orthorhombic structure (CaCl<Subscript>2</Subscript>-type) at 9.6 GPa, which is in good agreement with the experimental results. We predict a second structural phase transition from CaCl<Subscript>2</Subscript>- to fluorite-type structure at 89.6 GPa with a volume collapse of 7.3%, which is yet to be confirmed experimentally. Interestingly, CrO<Subscript>2</Subscript> shows half metallicity under ambient conditions. After the first structural phase transition from tetragonal to orthorhombic, half metallicity has been retained in CrO<Subscript>2</Subscript> and it vanishes at a pressure of 41.6 GPa. Ferromagnetism is quenched at a pressure of 65 GPa. Copyright EDP Sciences/Società Italiana di Fisica/Springer-Verlag 2008