Magnetic collapse and electronic phase transitions at high pressure in transition metal oxides

A review of electronic and magnetic phase transition in metal oxides with strong electron correlations (SEC) is given. The bandwidth control of the insulator gap is expected in the Hubbard model when the decreasing of the interatomic distance results in the bandwidth W(P) increase and at some critical value P-c W(P-c)similar to U and the Mott-Hubbard gap disappears. The other situation takes place in transition metal boroxides FeBO3 and GdFe3(BO3)(4), where the increase of crystal field parameter Delta(P) results in the high spin-low spin crossover. (c) 2005 Published by Elsevier B.V.