Magneto-electronic Properties of a Ferrimagnetic Semiconductor: The Hybrid Cupromanganite CaCu3Mn4O12

The mixed manganite-cuprate CaCu3Mn4O12 is found, using density functional methods, to be a narrow gap (90 meV calculated) ferrimagnetic semiconductor. Cu (formally S=1/2) antialigns with Mn (formally S=3/2), and the net spin moment is 9 \mu_B consistent with the formal spins. Holes have Cu d_{xy}-O p_{\sigma} (i.e. antibonding dp\sigma) character with spins aligned antiparallel to the net magnetization; electrons have the opposite spin and have mixed Cu d_{xy} - Mn e_g character. Thermally excited electrons and holes will each be fully spin polarized, but in opposite directions. The properties of this material are strongly tied to the distorted quadruple perovskite structure, which is closely related to the skutterudite structure. The observed resistivity, magnetoresistance, and magnetization are discussed in terms of our results.