Pressure induced state in the orthorhombic (Mn_1-xCo_x)₂P system

In this paper we present the results of ac susceptibility measurements of a (Mn_0.65Co_0.35)₂P sample under pressure up to 7.5 GPa. The pressure induced low temperature ferromagnetic state in pressures above 5-6 GPa was established. Theoretical analysis of the electronic band structure 'under pressure' was carried out by the Korringa-Kohn-Rostoker method incorporating the coherent potential approximation (KKR-CPA). We could conclude that the local magnetic moment decreases with pressure. Moreover, when external pressure is applied along the c-axis, in the case of manganese atoms placed at the tetrahedral site, the magnetic moment practically disappears, but in the case of Co decreases only slightly. This type of behavior may be responsible for the pressure induced phase transition from the antiferromagnetic (AF) state to the ferromagnetic (F) state. KKR-CPA electronic band structure calculations undertaken in the antiferromagnetic state are also presented from which it was found that the density of states (DOS) at the Fermi level varies with applied pressure in the opposite way, when accounting for F and AF states. The rapid decrease of DOS at E_F in the ferromagnetic (Mn_0.65Co_0.35)₂P additionally supports the experimentally observed pressure induced AF-F transition