Magnetic properties of iron sulfides doped with 3d transition-metals studied by Mossbauer spectroscopy

It is found by Mossbauer measurements on M0.025Fe0.975S (M = Se, Ti, V, Cr, Mn, Co, Ni, Cu) that the 3d transition-metal impurities influence the spin reorientation transitions of iron sulfide. It is noteworthy that both V0.025Fe0.975S and Co0.025Fe0.975S have Morin transition temperatures T-M which are distinctly different from that of FeS; furthermore, the directions of the T-M changes are opposite for V0.025Fe0.975S and Co0.025Fe0.975S. However, it is found that both the Neel temperature T-N and the alpha-transition temperature T alpha are almost unaffected by the 3d transition-metal impurities. A vanadium impurity of 2.5% of the metal atoms in the iron sulfide makes the crystallographic 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 V0.025Fe0.975S has a hysteresis width of 5 K. (c) 2005 Elsevier B.V. All rights reserved.