A Mössbauer study of amorphous Fe40Ni40B20

Abstract

Amorphous Fe40Ni40B20 (VITROVAC 0040) alloy has been investigated using 57Fe Mössbauer Spectroscopy. The Curie temperature Tc is found to be well defined and is 695 ± 1 K. The quadrupole splitting just above Tc is 0.64 mm sec-1. The crystallization temperature is 698 ± 2 K, close to but definitely above Tc. The average hyperfine field Heff(T) of the glassy state shows a temperature dependence of Heff(0)[1 - B 3 2(T/Tc) 3 2 - C 5 2(T/Tc) 5 2 - ...] indicative of the existence of spin wave excitations. The values of B 3 2 and C 5 2 are found to be 0.40 and 0.06, respectively, for T/Tc ≤ 0.72. At temperatures close to Tc, Heff(T) varies as (1 - T/Tc)β where β is one of the critical exponents and its value is found to be 0.29 ± 0.02. © 1982.