AF-FRI metamagnetic transition in itinerant Mn2-xCOxSb system:: high-field and high-pressure effects

The magnetization of Mn2-xCoxSb system with 0 less than or equal to x less than or equal to 0.35 has been measured under high magnetic fields up to 100 T and high pressure up to 12 kbar. Mn2Sb is a ferrimagnet and substitution of Co for Mn at 0.18 less than or equal to v less than or equal to 0.35 results in the appearance of the spontaneous first-order magnetic phase transition from ferrimagnetic (FRI) to antiferromagnetie (AF) state at T = T-1 with decreasing temperature at a critical Co concentration. Below T, a first-order field-induced AF-FRI transition is observed at a critical field B,. The critical field B, is found to decrease with increasing pressure applied at T = 4.2 K. The AF state which appeared for the compound with the critical concentration x = 0.18 can be transformed to the FRI one by the application of the high pressure of about 16 kbar by increasing the amount of FRI phase. Using the experimental data, the magnetic phase diagrams B-c-T-x and B-c-p-x are determined. The observed magnetic properties and magnetic phase diagrams of Mn2-xCoxSb are explained by the itinerant magnetism of d-electrons and by peculiarities of electronic structure. The itinerant nature of AF-FRI transition is confirmed by specific heat measurements in AF- and field-induced FRI states. (C) 2002 Published by Elsevier Science B.V.