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|Date and time:||12th Dec. (Fri.) 15:00〜|
|Place:||SPring-8 Kamitsubo Hall|
|Title:||High-field electron spin resonance study of electronic inhomogeneities in correlated transition metal compounds|
|Speaker:||Dr. Alexey Alfonsov (Kobe University)|
Electronic inhomogeneities play an important role in the definition of physical properties of correlated systems. To study these inhomogeneities one has to use local probe techniques which can distinguish electronic, magnetic and structural variations at the nanoscale. In the present work the high-field electron spin resonance technique (HF-ESR) is used to probe electronic and magnetic inhomogeneities in two transition-metal element based systems with very different properties. The first system is an iron based high-temperature superconductor, namely a member of a so called 1111-family, the GdO1-xFxFeAs compound. Our HF-ESR spectroscopy study on Gd3+ion has revealed that this material exhibits anisotropic interaction between Gd and Fe layers, which is frustrated in the absence of an external magnetic field. Moreover, the study of the superconducting samples has shown a coexistence of a static short range magnetic order with superconductivity up to high doping levels. The second system is a lightly hole doped cubic perovskite LaCoO3. Here, our HF-ESR investigation, complemented with static magnetometry, nuclear magnetic resonance and inelastic neutron scattering techniques, has established that the hole doping induces a strong interaction between electrons on neighboring Co ions which leads to a collective high-spin state, called a spin-state polaron. These polarons are inhomogeneously distributed in the nonmagnetic matrix, and seem to be building blocks for various phases at increased doping levels.