Nuclear resonant small-angle scattering for investigation of microstructures in electronic States

The measurement of the nuclear resonant small-angle scattering was achieved by scanning the position of a multi-element avalanche photodiode detector, detecting delayed nuclear resonant signal to investigate microstructures of the electronic states. The nuclear resonant small-angle scattering has been attempted to study the coexisting phase of superconductivity and magnetic order in an under-doped Fe-based superconductor, Ba_0.8K_0.2Fe₂As₂. Clear change was not observed in the exponent of the angular profile of the nuclear resonant small-angle scattering in the coexisting temperature. This fact implies the microstructure in the coexisting phase does not have an obvious typical scale but a complex spatial texture. Another attempt was performed for the microstructure in the magnetic properties in an anti-invar fcc Fe-Ni-C alloy to investigate mechanism of the anti-invar properties. An enhancement of the angular profile in a few tens of nm range was observed as decreasing the temperature down to a little below the Curie temperature. This fact implies the existence of the inhomogeneity of magnetically-ordered phase in this range of size, which may related to the anti-invar properties.