Electronic structure of heavy-fermion systems YbT2Zn20 (T=Fe, Co, Ru, Rh, Os, Ir)

Electronic band structure calculations were carried out for dilute rare earth bearing family of RT2Zn20 (R = Y, Yb, Lu, T = Fe, Co, Ru, Rh, Os, Ir) adopting the linear muffin-tin-orbital method in the atomic sphere approximation within the framework of the local spin-density approximation (LSDA). The Fermi energies in the 4f-itinerant band structures are found to be located in the immediate vicinity of the 4f-band of the j = 7/2 state with extremely narrow band width. In the YbA2Zn20 (A = Fe, Ru, and Os) compounds, the j = 7/2 bands are situated just below the Fermi level. In the YbB2Zn20 (B = Co, Rh, and Ir) compounds, the j = 7/2 bands touch the Fermi level. These trends of the 4f-bands are consistent with thermodynamic and transport properties. The calculated de Haas-van Alphen (dHvA) frequencies fairly well reproduce the data detected in pulsed fields directed along [110] and [111] directions for YbX2Zn20 (X = Fe, Co, and Rh), LuX2Zn20 (X = Fe and Co), and YCo2Zn20, although large dHvA frequencies more than 3.0x107 Oe for YbFe2Zn20, YbCo2Zn20, and LuCo2Zn20 are not found in present calculations. For YbIr2Zn20, detected angular dependences of dHvA frequencies are not explained by the 4f-itinerant LSDA band model. A small alternation so as to shift downward the Fermi level is necessary to fit to the experimental dHvA data. (author)