Dual nature of 3d electrons in YbT2Zn20 (T Co; Fe) evidenced by electron spin resonance

Abstract

The electron spin resonance experiments were carried out in the single crystals YbFe2Zn20. The observed spin dynamics is compared with that in YbCo2Zn20 and Yb2Co12P7 as well as with the data of inelastic neutron scattering and electronic band structure calculations. Our results provide direct evidence that 3d electrons are itinerant in YbFe2Zn20 and localized in YbCo2Zn20. Possible connection between spin paramagnetism of dense heavy fermion systems, quantum criticality effects, and ESR spectra is discussed.