Large Cyclotron Effective Masses in Antiferromagnet SmTi2Al20 Compared with Conventional Masses in Ferromagnet SmNi2Cd20 and Antiferromagnet SmPd2Cd20

We grew high-quality single crystals of a ferromagnet SmNi₂Cd₂₀, an antiferromagnet SmPd₂Cd₂₀, and an antiferromagnet SmTi₂Al₂₀ with the cubic cage structure by the self-flux method and carried out the de Haas–van Alphen experiment to detect the large cyclotron effective masses of the main Fermi surfaces. This is because these compounds are reported to possess large electronic specific heat coefficients of 100–200 mJ/(K²·mol). We have succeeded in detecting the main Fermi surfaces. The corresponding cyclotron mass of a so-called valence-fluctuating compound SmTi₂Al₂₀ is surprisingly large, revealing 26 m₀ (m₀: rest mass of an electron). In SmTi₂Al₂₀, no Curie–Weiss term is found in the magnetic susceptibility, and the −log T dependence of the electrical resistivity is observed at low temperatures. On the other hand, the conventional masses of 2.1 m₀ are obtained in SmNi₂Cd₂₀ and SmPd₂Cd₂₀, following the Curie–Weiss law in the magnetic susceptibility.