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

The payer presents the results of temperature (5-450 K) magnetic and Mossba uer 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 structure s of ferromagnetic and spin-glass types coexist. The latter is Mattis' spin glass (doubly degenerate), in which the magnetic moment of the Fe atom wit h 9 and more Sn atoms in the nearest environment is oriented in the opposit e direction to that of magnetization. The ground slate of Fe-Si alloys is f erromagnetic, with non-magnetic Fe atoms surrounded by 7 and more Si neares t neighbours appearing as Si content increase. On increasing the temperatur e of the alloys, apart from the long-range excitations, the collective shor t-range excitations appear in the magnetic matrix of a ground state, and th ey 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 excitation s appear at temperatures T greater than or equal to 0.7T(c), in the Fe-Sn a lloys they appear at much lon er temperatures T greater than or equal to 0. 3T(c). (C) 2000 Elsevier Science B.V. All rights reserved.