SHORT-TIME HIGH-TEMPERATURE ANNEALING OF FE(CUMO)SIB - A MOSSBAUER STUDY

The very soft magnetic properties of the Fe73.5Cu1Nb3Si13.5B9 (FINEMET ) alloy are due to a nanocrystalline structure built during the anneal ing of the as-quenched amorphous ribbon at suitable chosen temperature and time. In the nanocrystalline state, the samples consist of nanosc ale FeSi grains with diameters between 10 and 15 nm embedded in a rema ining amorphous matrix. The formation of the nanostructure is influenc ed by the elements Cu and Nb. In this contribution, Nb is replaced by Mo, an atom with a smaller diameter. The aim of this experimental stud y is to investigate the changes in the onset of nanocrystallization, t he microcrystallization and also the crystallization products due to t he replacement of Nb by Mo. The conventional Mossbauer effect on Fe-57 is used as a tool for phase analysis. The phase identification is don e via the hyperfine field values. We are able to perform well defined annealing procedures for short times, i.e., 15, 30, 60, 90, 120, 180, 300 and, for comparison, 3600 s. This time series was performed at a r ather high annealing temperature of 650 degrees C, After the annealing procedure, the samples were rapidly cooled down to room temperature. The Mossbauer spectra are collected after this procedure. (C) 1997 Els evier Science S.A.