149Sm synchrotron-radiation-based Mössbauer spectroscopy of Sm-based heavy fermion compounds
摘要
149Sm synchrotron-radiation-based Mössbauer spectroscopy has been applied to Sm-based heavy fermion intermetallics, SmTr2Al20 (Tr = Ti, V and Cr) and SmOs4Sb12. The isomer shifts obtained demonstrate that the Sm valence states in these compounds are intermediate. Since the difference of the isomer shifts in 22.502 keV 149Sm Mössbauer effect between Sm2+ and Sm3+ state is comparable to the 2nd order Doppler shift, consideration of the 2nd order Doppler shift is required to precisely discuss Sm valence state through the shifts of the Mössbauer spectra. In addition, the plots of the isomer shifts obtained by the Mössbauer spectroscopy against the Sm valence states estimated from Sm L-edge X-ray absorption spectroscopy exhibit a linear correlation except for that in SmOs4Sb12. This implies that the origin of the intermediate valence state in SmOs4Sb12 differs from that in SmTr2Al20 (Tr = Ti, V and Cr).