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

The paper presents the results of temperature (5–450K) magnetic and Mössbauer studies of nanocrystalline Fe100−xSnx (x=46, 55 and 62at%) and Fe100−xSix (x=33, 42 and 50at%) 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 Mössbauer 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.