Magnetic behaviour of high Si(Sn) concentration nanocrystalline Fe–Si and Fe–Sn alloys obtained by mechanical grinding

Abstract The paper presents the results of temperature (5–450 K) magnetic and Mossbauer studies of nanocrystalline Fe100−xSnx (x=46, 55 and 62 at%) and Fe100−xSix (x=33, 42 and 50 at%) obtained by mechanical grinding. It has been ascertained that in the ground state of Fe–Sn alloys the magnetic structures of ferromagnetic and spin-glass types coexist. The latter is Mattis’ spin glass (doubly degenerate), in which the magnetic moment of the Fe atom with 9 and more Sn atoms in the nearest environment is oriented in the opposite direction to that of magnetization. The ground state of Fe–Si alloys is ferromagnetic, with non-magnetic Fe atoms surrounded by 7 and more Si nearest neighbours appearing as Si content increase. On increasing the temperature of the alloys, apart from the long-range excitations, the collective short-range excitations appear in the magnetic matrix of a ground state, and they result in a non-magnetic component in the Mossbauer spectra. It has been found out that in contrast to Fe–Si alloys in which short-range excitations appear at temperatures T⩾0.7Tc, in the Fe–Sn alloys they appear at much lower temperatures T⩾0.3Tc.