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Semiconductive and Photoconductive Properties of the Single Molecule Magnets Mn12-Acetate and Fe8Br8

J. M. North·D. Zipse·N. S. Dalal·E. S. Choi·E. Jobiliong·J. S. Brooks·D. L. Eaton
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Abstract

Resistivity measurements are reported for single crystals of Mn12-Acetate and Fe8Br8. Both materials exhibit a semiconductor-like, thermally activated behavior over the 200-300 K range. The activation energy, Ea, obtained for Mn12-Acetate was 0.37 +/- 0.05 eV, which is to be contrasted with the value of 0.55 eV deduced from the earlier reported absorption edge measurements and the range of 0.3-1 eV from intramolecular density of states calculations, assuming 2Ea = Eg, the optical band gap. For Fe8Br8, Ea was measured as 0.73 +/- 0.1 eV, and is discussed in light of the available approximate band structure calculations. Some plausible pathways are indicated based on the crystal structures of both lattices. For Mn12-Acetate, we also measured photoconductivity in the visible range; the conductivity increased by a factor of about eight on increasing the photon energy from 632.8 nm (red) to 488 nm (blue). X-ray irradiation increased the resistivity, but Ea was insensitive to exposure.

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J. M. North, D. Zipse, N. S. Dalal, E. S. Choi, E. Jobiliong, J. S. Brooks, D. L. Eaton. 2003-01-27. Semiconductive and Photoconductive Properties of the Single Molecule Magnets Mn12-Acetate and Fe8Br8. https://arxiv.org/abs/cond-mat/0301515

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