Nonlinear paramagnetic magnetization in the mixed state of CeCoIn_5

Torque and magnetization measurements in magnetic fields $H$ up to 14 T were performed on CeCoIn${}_5$ single crystals. The amplitude of the paramagnetic torque shows an $H^{2.3}$ dependence in the mixed state and an $H^2$ dependence in the normal state. In addition, the mixed-state magnetizations for both $H\parallel c$ and $H\parallel ab$ axes show anomalous behavior after the subtraction of the corresponding paramagnetic contributions as linear extrapolations of the normal-state magnetization. These experimental results point towards a nonlinear paramagnetic magnetization in the mixed state of CeCoIn${}_5$, which is a result of the fact that both orbital and Pauli limiting effects dominate in the mixed state.