Electronic Structure of Heavy-Fermion Systems Yb$T_{2}$Zn20 ($T = \text{Fe}$, Co, Ru, Rh, Os, Ir)

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Electronic band structure calculations were carried out for dilute rare earth bearing family of $RT_{2}$Zn20 ($R = \text{Y}$, Yb, Lu, $T = \text{Fe}$, 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 Yb$A_{2}$Zn20 ($A = \text{Fe}$, Ru, and Os) compounds, the $ j = 7/2$ bands are situated just below the Fermi level. In the Yb$B_{2}$Zn20 ($B = \text{Co}$, 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 Yb$X_{2}$Zn20 ($X = \text{Fe}$, Co, and Rh), Lu$X_{2}$Zn20 ($X = \text{Fe}$ and Co), and YCo2Zn20, although large dHvA frequencies more than $3.0 \times 10^{7}$ 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.
2010-12-15