Magnetic Properties of Iron Sulfides Doped With 3-D Transition-Metals

It is found by Mossbauer measurements on M_0.025Fe_0.975S (M=Sc , Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) that the 3-D-transition metal impurities profoundly affect both the structural phase and the spin rotation transitions of iron sulfide. It is noteworthy that both V_0.025Fe_0.975S and Co_0.025Fe_0.975S have Morin transition temperatures T_M which are distinctly different from that of FeS; furthermore, the directions of changes of T_M are opposite for V_0.025Fe_0.975S and Co_0.025Fe_0.975S . A vanadium impurity of 2.5% of the metal atoms in the iron sulfide makes the structure transition take place rapidly in a narrow temperature region of about 15 K, while the alpha transition in FeS takes place over a wide temperature range of about 200 K. It is also found that the alpha transition for V_0.025Fe_0.975S has a hysteresis width of 5 K. It is noteworthy that the structural transition is independent of the lattice parameters while the spin-rotation transition is dependent on them.