Positive and negative magnetocaloric effects in CeSi

We present a study of the magnetocaloric effect (MCE) in the commensurate antiferromagnet CeSi. We show that the MCE exhibits both positive and negative components, the former indicative of a magnetic configurational entropy increases upon isothermal magnetisation. We describe the Hamiltonian of the system as a simple model antiferromagnetic Hamiltonian where spins are ferromagnetically aligned in the ac-plane, while planes are weakly antiferromagnetically coupled along the b-axis (consistent with μSR experimental results). We show that reproduces both the positive and the negative MCE for applied fields up to 30 kOe, while in larger fields the magnitude of the negative component (indicative of an overall suppression of magnetic configurational entropy) is larger than expected from our model.