Phonon anomalies and the magnetic transition in pure and Cr-doped V/sub 2/O/sub 3/

Journal Article · Tue Dec 01 04:00:00 EST 1987 · Phys. Rev. B: Condens. Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.36.8675· OSTI ID:5679648

Yethiraj, M; Werner, S A; Yelon, W B; Honig, J M

We have studied the lattice dynamics, the magnetic ordering and excitations, and the crystallographic distortions associated with the metal-insulator transitions in pure and Cr-doped vanadium sesquioxide using neutron-scattering techniques. In the paramagnetic metallic phase of pure V/sub 2/O/sub 3/ and in the higher-temperature paramagnetic metallic phase of 1.5-at. %-Cr-doped V/sub 2/O/sub 3/ we see an anomalous splitting of the transversely polarized acoustic phonon mode, propagating along the hexagonal (hh0) direction near the center of the Brillouin zone. Upon lowering the temperature, a substantial softening of a large portion of the transverse acoustic branch in the (00l) direction is observed in Cr-doped samples in the paramagnetic insulating phase as the transition to the antiferromagnetic insulating phase is approached. The loss of antiferromagnetic order with increasing temperature in 3-at. %-Cr-doped and 6-at. %-Cr-doped samples appears to be nearly continuous. The temperature dependence of the spin-wave energy gap in the 3-at. %-Cr-doped sample appears to approach zero continuously up to the Neel temperature. The monoclinic distortion of the trigonal phase at this transition is much reduced in the 6-at. %-Cr-doped sample compared to pure V/sub 2/O/sub 3/. These and other results are described in detail, and discussed in connection with the recent theoretical work on metal-insulator transitions.

• Research Organization: Physics Department and Research Reactor Facility, University of Missouri-Columbia, Columbia, Missouri 65211
• OSTI ID: 5679648
• Journal Information: Phys. Rev. B: Condens. Matter; (United States), Journal Name: Phys. Rev. B: Condens. Matter; (United States) Vol. 36:16; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
ALLOYS
BRILLOUIN ZONES
CHALCOGENIDES
CHROMIUM ADDITIONS
CHROMIUM ALLOYS
COHERENT SCATTERING
COLLECTIVE EXCITATIONS
DIFFRACTION
DOPED MATERIALS
ENERGY GAP
ENERGY-LEVEL TRANSITIONS
EXCITATION
LATTICE VIBRATIONS
MAGNETIC PROPERTIES
MATERIALS
NEUTRON DIFFRACTION
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
PHONONS
PHYSICAL PROPERTIES
QUASI PARTICLES
SCATTERING
SPIN WAVES
TEMPERATURE DEPENDENCE
TRANSITION ELEMENT COMPOUNDS
VANADIUM COMPOUNDS
VANADIUM OXIDES
ZONES