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Metamagnetic transitions in the novel spin-triplet superconductor UTe$_2$ were investigated through the newly developed simultaneous measurements of magnetization and sample temperature for the field along the orthorhombic $b$-axis and close to the [011] direction, where reentrant superconductivity (RSC) is detected below and above the first-order metamagnetic transition field $H_{rm m}$. Combining the Maxwells relation and the Clausius-Clapeyron equation, we obtained the field dependence of Sommerfeld coefficient $gamma$ through the first-order metamagnetic transition. A significant enhancement of the effective mass toward $H_{rm m}$ were detected for both field directions. On the other hand, above $H_{rm m}$, the effective mass discontinuously decreases for $H~||~b$, while it discontinuously increases for $H~||~sim [011]$, which seems to make a crucial role for the RSC.
We report the measurements of anisotropic magnetization and magnetoresistance on single crystals of EuFe$_2$As$_2$, a parent compound of ferro-arsenide high-temperature superconductor. Apart from the antiferromagnetic (AFM) spin-density-wave transiti
By means of the magnetocaloric effect, we examine the nature of the superconducting-normal (S-N) transition of Sr2RuO4, a most promising candidate for a spin-triplet superconductor. We provide thermodynamic evidence that the S-N transition of this ox
We investigate the specific heat of ultra-pure single crystals of Sr2RuO4, a leading candidate of a spin-triplet superconductor. We for the first time obtained specific-heat evidence of the first-order superconducting transition below 0.8 K, namely d
We report the synthesis and physical properties of single crystals of stoichiometric BaNi2As2 that crystalizes in the ThCr2Si2 structure with lattice parameters a = 4.112(4) AA and c = 11.54(2) AA. Resistivity and heat capacity show a first order pha
We investigated the magnetic field dependence of the superconducting phase transition in heavy fermion CeCoIn_5 (T_c = 2.3 K) using specific heat, magneto-caloric effect, and thermal expansion measurements. The superconducting transition becomes firs