ELECTRONIC, STRUCTURAL, AND MAGNETIC PROPERTIES OF TRANSITION-METAL INSULATORS AT VERY HIGH PRESSURES

摘要

By simultaneously combining the methods of X-ray diffraction for structural phase transitions and EOS measurements, ~(57)Fe Mossbauer spectroscopy (MS) as a site-sensitive probe, and resistivity measurements for studying insulating-metal transitions we are able to study the effect of extreme pressures and at varying temperature on magnetic and electronic properties of Transition Metal Compounds (TMC). Studies are earned out with specially tailored diamond anvils and diamond anvil cells, reaching pressures beyond 100 GPa. Our studies allow investigating the most basic phenomenon of quantum effect of magnetism in insulating antiferromagnets, the Mott insulators: the high to low spin crossovers, quenching of magnetic moments' orbital term, and the collapse of the Mott-Hubbard state. Examples of these phenomena will be given in cases of ferrous and ferric o oxides, ferrous-halides and the rare-earth iron perovskites.