The pressure-induced Mott Transition in transition-metal iodides

Conference · Tue Jan 01 00:00:00 EST 1991

DOI:https://doi.org/10.1063/1.350089· OSTI ID:5750191

Pasternak, M P ^[1]; Taylor, R D ^[2]; Jeanloz, R ^[3]

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1. Tel Aviv Univ. (Israel). School of Physics and Astronomy
2. Los Alamos National Lab., NM (USA)
3. California Univ., Berkeley, CA (USA). Dept. of Geology and Geophysics

Many of the Transition Metal (TM) compounds, because of exchange and correlation interactions within the narrow and poorly overlapping d-bands, become antiferromagnetic insulators, the Mott Insulators (MI). The properties of the MI and their gradual transition into the non-correlated metallic state (the Mott Transition) are of crucial important for the elucidation of HTS materials features in particular and to magnetism in general. The transition of the MI into a metal can be achieved either by doping or by high pressure. To yield the definitive data on the Mott transition high pressure work on well characterized materials should be sought. The present studies provide for the first time extensive information on the Mott-Hubbard gap closure induced by high pressure. High pressure studies using Diamond Anvil Cells were conducted in several (TM)I{sub 2} compounds. They all have layered structures and other antiferromagnetically at ambient pressure. {sup 129}I Moessbauer Spectroscopy (MS) was used to study the properties of the (TM){sup 2+} sublattice magnetization as a function of pressure and temperature, and X-ray diffraction was used to look for possible crystallographic transitions and to obtain the equation of state. Results show that the high pressure transition at P{sub c} from a magnetic to a non-magnetic state is not accompanied by crystallographic changes. Previous studies{sup 1} with NiI{sub 2} have confirmed the presence of a metallic state at P > P{sub c}. Inherent to the pressure behavior of the magnetic state is the gradual increase of T{sub N} in all cases and a slight increase in the TM{sup 2+} moments with pressure increase. The collapse of the magnetic state is abrupt for some cases (NiI{sub 2}) and gradual for others (CoI{sub 2}), indicative of different band-overlap mechanisms. 2 refs., 5 figs.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE; USDOE, Washington, DC (USA)
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 5750191
• Report Number(s): LA-UR-91-1538; CONF-910608-4; ON: DE91013671
• Resource Relation: Journal Volume: 70; Journal Issue: 10; Conference: 5. joint magnetism and magnetic materials (MMM/INTERMAG) conference, Pittsburgh, PA (USA), 18-21 Jun 1991
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
COBALT IODIDES
SPECTROSCOPY
X-RAY DIFFRACTION
NICKEL IODIDES
TRANSITION ELEMENTS
ELECTRONIC STRUCTURE
ANTIFERROMAGNETISM
BAND THEORY
ELECTRICAL INSULATORS
EQUATIONS OF STATE
MAGNETIC INSULATION
MAGNETIZATION
MEETINGS
PRESSURE EFFECTS
COBALT COMPOUNDS
COHERENT SCATTERING
DIFFRACTION
ELECTRICAL EQUIPMENT
ELEMENTS
EQUATIONS
EQUIPMENT
HALIDES
HALOGEN COMPOUNDS
IODIDES
IODINE COMPOUNDS
MAGNETISM
METALS
NICKEL COMPOUNDS
SCATTERING
TRANSITION ELEMENT COMPOUNDS
360102* - Metals & Alloys- Structure & Phase Studies
360104 - Metals & Alloys- Physical Properties