Dresden 2006 – wissenschaftliches Programm
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MA: Magnetismus
MA 5: Spin-Structures and Magnetic Phase Transitions I
MA 5.6: Vortrag
Montag, 27. März 2006, 11:30–11:45, HSZ 403
LDA+U Picture of the Moment and Volume Collapse under Pressure in MnO — •Deepa Kasinathan1, Jan Kunes1, Klaus Koepernik2, and Warren Pickett1 — 1University of California,Davis, CA 95616 — 2IFW Dresden, P.O.Box 270116, D-01171, Dresden, Germany
The transition metal monoxide MnO crystallizes in the rock-salt structure and is a high-spin antiferromagnetic insulator at low temperatures. Under pressure, experimentally it is observed to undergo a metal-insulator transition after a structural change to the nickel arsenide phase. As the first step in a concerted effort to obtain a realistic theory of the pressure behavior of MnO, we have performed full potential local orbital (FPLO) LDA+U calculations in the rock-salt phase. Within the rocksalt phase we obtain a first order moment and volume collapse at specific volume V/V0 ≈ 0.61, very close to the experimental volume. The moment collapse is from high spin state 5/2 to a low spin state 1/2, along with a 8% decrease in volume. The magnetic transition is mainly governed by the oxygen coordination. The strong influence of symmetry-lowering (cubic to rhombohedral) by antiferromagnetism is noticed with the single occupancy of the five 3d orbitals before and after collapse ( i.e. total L = 0 ). Calculations in the high pressure regime shows that the system stabilizes in the antiferromagnetic NiAs structure, in par with the observed experimental results.