Behavior of antiferromagnetic MnCoSi in a magnetic field under pressure

Experimental data on magnetization of the antiferromagnetic (AFM) polycrystalline samples in the temperature range of 20-300 K, for pressures of 2 kbar and in magnetic field of 300 kOe, are presented in the paper. In the fields of 250 kOe, the magnetization curve demonstrates a jump explained by exchange-interaction sign change. In the region of 50-70 kOe, on the differential susceptibility versus magnetic field curve, there is a break of the 2nd order corresponding to the anomalous behavior of the magnetization. The obtained results were processed on the basis of the phenomenological Landau theory. It is shown that the ferromagnetic vector occurrence is forced during the formation of AFM spiral structure. The behavior of thermodynamic potential factors has been determined. Three more anomalies have been revealed and explained by a jump-like magnetization change of the Co-subsystem. (C) 2011 Elsevier B.V. All rights reserved.