Magnetic phases of $M_xAs_y$ (M=Co, Fe, Mn) compounds

We present theoretical calculations of $X_xAs_y$, (X = Co, Fe, Mn) in different structures in order to understand how the As surrounding influence the stability of the magnetic phases. We analyse the quenching of the magnetic moment of the ferromagnetic phases in terms of the pd+hybridisation between the magnetic ion and As. A simplified model of the quenching is suggested and the dependence on the number of As neighbours and nearest neighbour distance is investigated.