Pressure-induced Phonon Softenings and the Structural and Magnetic Transitions in CrO${}_2$

Abstract

To investigate the pressure-induced structural transitions of chromium dioxide (CrO${}_2$), phonon dispersions and total energy band structures are calculated as a function of pressure. The first structural transition has been confirmed at P$\approx$ 10 GPa from the ground state tetragonal CrO${}_2$ (t-CrO${}_2$) of rutile type to orthorhombic CrO${}_2$ (o-CrO${}_2$) of CaCl${}_2$ type. The half-metallic property is found to be preserved in o-CrO${}_2$. The softening of Raman-active B${}_{1g}$ phonon mode, which is responsible for this structural transition, is demonstrated. The second structural transition is found to occur for P$\ge$ 61.1 GPa from ferromagnetic (FM) o-CrO${}_2$ to nonmagnetic (NM) monoclinic CrO${}_2$ (m-CrO${}_2$) of MoO${}_2$ type, which is related to the softening mode at {\bf q} = R(1/2,0,1/2). The third structural transition has been newly identified at P= 88.8 GPa from m-CrO${}_2$ to cubic CrO${}_2$ of CaF${}_2$ type that is a FM insulator.

References in corpus (3)

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• Half-metallic ferromagnets: From band structure to many-body effects
• The metal-insulator transitions of VO2: A band theoretical approach

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• Ferromagnetic Type-II Weyl Semimetal in Pyrite Chromium Dioxide
• Lattice dynamics and structural transition of the hyperhoneycomb iridate $\beta$-Li${}_2$IrO${}_3$ investigated by high-pressure Raman scattering