Mott insulator to correlated metal: Optical study ofLa1−xTiO

Abstract

The room-temperature reflectance of a well-characterized series of samples (x-ray, neutron activation and thermigravimetric analyses, resistivity, magnetization) in the Lal "Ti03 system has been measured between 50 and 40000 cm on samples ranging from the antiferromagnetic insulating (LaTi03) to the metallic (Lao 88Ti03}part of the phase diagram. The electronic portion of the low-frequency optical conductivity increases with frequency at the lowest frequencies, similar to several barely metallic systems.This non-Drude behavior can be modeled as the sum of the two low-frequency oscillators, a Drude contribution that increases systematically with doping and a broad midinfrared continuum. The midinfrared band, which Inay be associated with transitions across the Hubbard gap, persists in highly doped samples in agreement with theoretical predictions. If one assumes a single low-frequency component with frequency-dependent scattering rate, one finds a negative mass enhancement below 150 cm ' in metallic samples close to the metal-insulator phase boundary.

Magnetic and Structural Studies of La1−xSmxTiO3(0≤x≤1)

“…The system loses magnetic ordering and changes into a paramagnetic metal by slight oxidation of the Ti ions, caused by nonstoichiometry of the oxygen content (3) by substitution of La> for Sr> ions (La \V Sr V TiO ) (3, 4), or by a slight La deficiency (5,6). As a different approach to this system, in the present work, we prepared a solid solution of La \V Sm V TiO (04x41) to elucidate the effects of lanthanide substitution on its structural and magnetic properties.…”

Meta–Insulator Phenomena in Strongly Correlated Oxides. The Vacancy-Doped Titanate Perovksites, Nd1−xTiO3 and Sm1−xTiO3

“…One set of materials that has drawn much interest is the¸nTiO series, where¸n is a rare earth and Ti has con"guration 3d.The MHI character of these materials has been well established by optical measurements that clearly show that ';'= (6). The MH gap can be tuned by changing the¸n ion, the gap magnitude decreasing with increasing¸n> radius (7). This is best understood in terms of the crystal structure of these compounds in which the Ti}O}Ti bond angle, which controls the bandwidth, =, decreases with decreasing¸n> radius (8).…”

The Structural and Magnetic Properties of Nd1−xTiO3forx= 0, 0.05, and 0.10

“…Members belonging to this family Nd 1Ϫx TiO 3 system, using the highly correlated La 1Ϫx TiO 3 of compounds possess the orthorhombically distorted series of compounds. This system was investigated by CranGdFeO 3 -type structure belonging to the space group dles et al (11) and MacEachern et al (12), whose investigaPnma. In general, these compounds are semiconducting tions encompassed the composition range 0 Յ x Յ 0.33.…”