Low-temperature magnetic behaviour in amorphous and nanocrystalline Fe-Nb-B alloys

The low-temperature magnetic behaviour is studied in a series of heat-treat ed amorphous and nanocrystalline Fe80.5Nb7B12.5 samples with different volu me fractions of crystalline phase, The measurements of coercivity, initial susceptibility and magnetostriction have been performed in a temperature ra nge between 1.5 and 300 K. The coercivity of nanocrystalline samples shows a minimum versus measuring temperature. The temperature of this minimum is shifted to lower temperatures with an increasing volume fraction of crystal line phase. A significant magnetic hardening characterized by abrupt upturn of coercivity is reported for all nanocrystalline samples in the temperatu re range below 30 K. The role of different factors in determining the low-t emperature magnetic behaviour is discussed. (C) 2000 Elsevier Science B.V, All rights reserved.