Magnetotransport properties and magnetostructural phenomenon in single crystals of La0.7(Ca1-ySry)0.3MnO3 -: art. no. 024421

The magnetotransport and magnetostructural properties of La-0.7(Ca1-ySry)(0.3)MnO3 (0 less than or equal to y less than or equal to 1) are studied. We investigate the variation in magnetoresistance (MR) with y and the field-induced structural transition at gamma similar to0.5 by using single crystals prepared by the floating-zone method. With the increase in y the colossal MR behavior at y similar to0 is transformed to a rather canonical MR (a MR free from lattice effects) at y=1. The coefficient C in the empirical relation that rho (M)/rho (0) = exp[-C(M/M-s)(2)] (M and M-s being the magnetization and its zero-temperature saturation value) shows a significant change with gamma, attainable for example, from 7.6 at y=0.1 to 2.3 at y=0.7. As an example of the magnetoswitching of a crystal structure around room temperature, the structural-phase transition induced by an external magnetic field is investigated for crystals with y similar to0.5. Structural-phase diagrams of the magnetic field vs temperature plane are given.