Transport and magnetic properties of a Mott-Hubbard system whose bandwidth and band filling are both controllable: R{sub 1{minus}x}Ca{sub x}TiO{sub 3+y/2}

Journal Article · Wed Oct 01 04:00:00 EDT 1997 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.56.10145· OSTI ID:543824

Katsufuji, T; Taguchi, Y; Tokura, Y ^[1]

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1. Department of Applied Physics, University of Tokyo, Tokyo 113 (Japan)

Transport and magnetic properties of R{sub 1{minus}x}Ca{sub x}TiO{sub 3+y/2} have been systematically investigated varying the one-electron bandwidth (W) and the band filling (n=1{minus}{delta}), which can be controlled by the R-dependent lattice distortion and by the Ca content x and/or oxygen offstoichiometry y ({delta}=x+y), respectively. The end compound RTiO{sub 3} is a 3d{sup 1} Mott-Hubbard insulator and its charge-gap magnitude increases with decreasing ionic radius of R, i.e., an increase of electron correlation (U/W) in proportion with (U/W){minus}(U/W){sub c}, where (U/W){sub c} is the critical value for the (hypothetical) n=1 Mott transition. Such a Mott insulator is transformed to a correlated metal by substitution of R with Ca (hole doping), and the nominal hole concentration required for the insulator-metal transition ({delta}{sub c}) increases in proportion with (U/W){minus}(U/W){sub c}. Concerning magnetism, RTiO{sub 3} with R=La, Pr, Nd, and Sm, shows the antiferromagnetic ordering and its N{acute e}el temperature (T{sub N}) decreases with smaller R. T{sub N} also decreases with Ca doping, but remains finite up to the metal-insulator phase boundary. On the basis of these results, electronic phase diagrams are derived for a series of titanates as an electron-correlated system with changes of two parameters, i.e., the strength of electron correlation and band filling. Possible origins of the insulating state with finite hole doping are also discussed in terms of the kinetic energy of doped carriers in the Mott-Hubbard insulator. {copyright} {ital 1997} {ital The American Physical Society}

• OSTI ID: 543824
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 16 Vol. 56; ISSN PRBMDO; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ANTIFERROMAGNETIC MATERIALS
BAND THEORY
CALCIUM OXIDES
ELECTRIC CONDUCTIVITY
ELECTRON CORRELATION
HOLES
LANTHANUM OXIDES
MAGNETIC PROPERTIES
NEEL TEMPERATURE
NEODYMIUM OXIDES
PRASEODYMIUM OXIDES
SAMARIUM OXIDES
STOICHIOMETRY
TITANIUM OXIDES