Resistivity and Electronic Structure in an 1D-Magnet VOMoO_4 : Condensed Matter: Structure, etc.

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Polycrystal of VOMoO_4 has been synthesized by sintering. The electrical resistivity, p, was measured with and without magnetic field down to 77K. The numerical value of p is about 5.4Ω・m at 300 K. The temperature dependent behavior is like as a semiconductor, but the Arhenius plot does not give any constant carriers' excitation energy. Above 100K p behaves as T^<-n> with n of about 5. Magnetic field up to 1 T gives little magnetoresistance and no Hall effect down to 77.2K. That means the very small mobility of carriers, and suggests the importance of electron-phonon interaction giving the heavy effective mass to carriers. Discussion was made about the relation to the structural instability of crystal, hence, phonon and magnetic instability. Estimation of the electronic state density was tried by molecular orbital calculation with X_α method. It was made sure that only V ions carry the spins. The shape and width of valence band was reasonable compared to measured ones. Energy gap at Fermi level could not be reproduced without electron-phonon interaction term. It was concluded that the current carriers are heavy polarons, whose mobility changes with temperature depending on the change of crystal local symmetry.
社団法人日本物理学会の論文
2000-12-15