Pressure-Induced Release of Magnetic Frustration in a Quasi-Kagome Antiferromagnet YbAgGe(Condensed matter: electronic structure and electrical, magnetic, and optical properties)

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We report on specific-heat measurements under various pressures up to 3.2GPa for a heavy-fermion antiferromagnet YbAgGe with a quasi-kagome lattice of Yb ions. For 0.5<P<P^*=1.6GPa, the magnetic transition temperature T_M remains constant at 0.85K, while above P^* the T_M increases linearly with a slope of 0.52K/GPa. Concomitantly, the specific-heat anomaly at T_M converts from a first-order type sharp peak to a second-order type jump. The magnetic entropy at T_M rises for P>P^*, whereas the Kondo temperature T_K does not change, contrary to the behavior expected from the Doniach phase diagram. These findings suggest that the sudden rise of T_M(P) for P>P^* is not due to the lowering of T_K but the release of the magnetic frustration.
社団法人日本物理学会の論文
2008-02-15