Thermal Transport in Nd-doped CeCoIn$_5$

Heavy-fermion superconductor CeCoIn$_5$ shows spin-density-wave (SDW) magnetic order in its superconducting state when a high magnetic field is applied. In this $Q$-phase, the antiferromagnetic order has a single ordering wave vector, and switches its orientation very sharply as magnetic field is rotated within the $ab$-plane around the [100] (anti-nodal) direction. This hypersensitivity induces a sharp jump of the thermal conductivity. Recently, the SDW with the same ordering wave vector was observed in Nd-doped CeCoIn$_5$ in zero magnetic field. We have measured the thermal conductivity of 5\% Nd-doped CeCoIn$_5$ in the magnetic field rotating within the $ab$-plane. The anisotropy is significantly smaller in the doped material, and the switching transition is much broader. The superconducting transition near $H_{c2}$ is first order, as for the pure CeCoIn$_5$, which indicates the Pauli limited superconductivity.