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Magnetism Close to the Metal-Insulator Transition in V 2 O 3

Magnetism Close to the Metal-Insulator Transition in V 2 O 3. Collin Broholm * Johns Hopkins University and NIST Center for Neutron Research. The Metal-Insulator Transition in V 2 O 3 Metallic V 2-y O 3 - Quantum critical heavy fermions Insulating (V 1-x Cr x ) 2 O 3

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Magnetism Close to the Metal-Insulator Transition in V 2 O 3

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  1. Magnetism Close to the Metal-Insulator Transition in V2O3 Collin Broholm* Johns Hopkins University and NIST Center for Neutron Research The Metal-Insulator Transition in V2O3 Metallic V2-yO3 - Quantum critical heavy fermions Insulating (V1-xCrx)2O3 - Coupled orbital and spin degrees of freedom Summary * Supported by the NSF through NSF DMR-9453362

  2. Alloying and Pressure effects in V2O3 • Cr-doping (3d3) More Insulating • Add a site to which 3d electrons cannot hop • Ti-doping (3d1) More metallic • Add a site to which 3d electrons can hop • Vacancy doping V2-yO3 More metallic • Add holes to 3d bands • Hydrostatic Pressure More metallic • Counteract lattice expansion in insulator • Increase orbital overlap thus decrease U/W

  3. Collaborators Wei Bao Los Alamos National Laboratory G. Aeppli NEC Research Institute S. A. Carter U. C. Santa Cruz P. Dai Oak Ridge National Laboratory T. F. Rosenbaum University of Chicago J. M. Honig Purdue University P. Metcalf Purdue University S. F. Trevino U. S. Army Research Lab and NIST • Experiments performed at • NIST Center for Neutron Research • HFIR, Oak Ridge National Laboratory • ISIS Facility, Rutherford Appleton Laboratory

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  5. Conclusions • Weakly doped V2O3 can lie on either side of an electron correlation induced Metal-Insulator Transition • Metallic V2-yO3 • “Heavy” Fermion system (vf=104 m/s). • Fermi surface nesting apparent in broad T-range. • Weak low T SDW and partially gapped Fermi surface almost quantum critical metal. • Moriya SCR theory provides Quantitative link between dynamical and thermal properties. • Insulating (V1-xCrx)2O3 • Local Structural and Orbital degrees of freedom couple to the spin system and limit correlation length at high T, • These degrees of freedom order for T<180 K at which point long range spin order and coherent spin waves develop.

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