Metamagnetic Behavior in Heavy-Fermion Compound YbIr2Zn20

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The metamagnetic behavior in the heavy-fermion compound YbIr2Zn20 with a cubic structure was studied by magnetization, de Haas–van Alphen (dHvA) oscillation, magnetoresistance, specific heat, thermal expansion, and magnetostriction measurements in single-crystalline samples. A metamagnetic anomaly at $H_{\text{m}} \simeq 100$ kOe was found to exist in all field directions in the cubic crystal structure. The cyclotron effective mass $m_{\text{c}}^{*}$, the coefficient $A$ in the Fermi liquid relation of electrical resistivity $\rho=\rho_{0} + AT^{2}$, and the electronic specific heat coefficient $C/T$ indicate a peak at the metamagnetic field $H_{\text{m}}$. The negative thermal expansion and negative volume magnetostriction suggest that the valence of the Yb ion gradually changes from a 4f-itinerant state to a trivalent state with increasing magnetic field, and an almost trivalent state is realized above the metamagnetic field $H_{\text{m}}$. On the other hand, the topology of the Fermi surface is approximately unchanged below and above $H_{\text{m}}$ in the dHvA experiment.
2010-06-15