Structural, Electronic, and Magnetic Properties of Lanthanum
Abstract
We report on the properties of La_ {rm x}Sr_{rm 1-x}VO_3 which has a phase diagram which is similar to Sr doped La _2CuO_4 in that it too shows a composition induced insulator to metal transition with strontium doping. In addition, the insulating compositions in the vanadium based system are antiferromagnetic and the La_{rm x}Sr _{rm 1-x}VO _3 system has a perovskite structure. These features are reminiscient of the properties of the high -T_{rm c} cuprate superconductors. This makes La_{rm x}Sr_{rm 1-x} VO_3 a candidate for a detailed study of its properties in order to gain a greater insight into the mechanisms at play in the high-T_ {rm c} cuprate superconductors. Magnetic susceptibility, X-ray powder diffraction and ^{51}V NMR Knight shift and relaxation rates, T_sp{1 }{-1} and T_sp{2 }{-1}, are reported as functions of temperature and composition in La_{ rm x}Sr_{rm 1-x}VO_3. A combined analysis of the susceptibility and the ^ {51}V NMR data yields values of the density of states D(epsilon_{rm f}) and for the enhancement of the uniform susceptibility. These are indicative of a strongly exchange enhanced narrow d-band metal for x < 0.7. No evidence was found for antiferromagnetic spin fluctuations in the metallic phase nor for superconducting behaviour, in these compounds. We have extensively investigated the properties of LaVO_3. We have observed diamagnetism in this compound, which is an antiferromagnetic insulator, below the Neel temperature under field-cooled conditions. We observe hysteresis in magnetization versus applied field M(II) isotherms below the Neel temperature. LaVO _3 has a ferromagnetic component to the spin ordering, due to canting of spins and/or ferrimagnetism. Four - probe resistivity measurements rule out the possibility of superconductivity and the diamagnetism appears to be associated with ferrimagnetism in this compound. The susceptibility was found to be different below the Neel temperature under field-cooled (FC) and zero-field-cooled (ZFC) conditions. From our ^{51}V NMR measurements on LaVO_3 we associate the kink in susceptibility with magnetic ordering.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- 1991
- Bibcode:
- 1991PhDT.......229M
- Keywords:
-
- X) STRONTIUM(1-X) VANADIUM OXYGEN(3) (0 LESS THAN OR EQUAL TO X LESS THAN OR EQUAL TO 1.0) (ELECTRONIC PROPERTIES;
- LANTHANUM STRONTIUM VANADIUM OXIDE;
- Physics: Condensed Matter