Grazing-incidence synchrotron-radiation ⁵⁷Fe-Mössbauer spectroscopy using a nuclear Bragg monochromator and its application to the study of magnetic thin films

Energy-domain grazing-incidence ⁵⁷Fe-Mössbauer spectroscopy (E-GIMS) with synchrotron radiation (SR) has been developed to study surface and interface structures of thin films. Highly brilliant ⁵⁷Fe-Mössbauer radiation, filtered from SR by a ⁵⁷FeBO₃ single-crystal nuclear Bragg monochromator, allows conventional Mössbauer spectroscopy to be performed for dilute ⁵⁷Fe in a mirror-like film in any bunch-mode operation of SR. A theoretical and experimental study of the specular reflections from isotope-enriched (⁵⁷Fe: 95%) and natural-abundance (⁵⁷Fe: ∼2%) iron thin films has been carried out to clarify the basic features of the coherent interference between electronic and nuclear resonant scattering of ⁵⁷Fe-Mössbauer radiation in thin films. Moreover, a new surface- and interface-sensitive method has been developed by the combination of SR-based E-GIMS and the ⁵⁷Fe-probe layer technique, which enables us to probe interfacial complex magnetic structures in thin films with atomic-scale depth resolution.