Mössbauer study of amorphous Fe 73.5Cu 1Nb 3Si 13.5B 9 alloy

Abstract

This paper reports a Mössbauer study of amorphous Fe 73.5Cu 1Nb 3Si 13.5B 9 alloy between 10 and 673 K. The Curie temperature T C is found to be 620±1 K. The temperature dependence of the reduced average hyperfine field can be explained on the basis of Handrich's model of amorphous ferromagnetism, in which the parameter δ, which measures fluctuations in the exchange interactions, is assumed to have a temperature dependence δ = 0.525 + 0.208–0.551 2, where t is T/ T C. At low temperatures, the average hyperfine field H eff( T) can be fitted to H eff (0)( 1 -b 3 2 (T/T C 3 2 ) , with H eff(0) = 255 ± 1 kOe and b 3 2 = 0.43 over a large temperature range ( T/ T C < 0.5), which indicates the presence of long-wavelength spin-wave excitations in the amorphous alloy. At temperatures below T C, the reduced average hyperfine field varies as D(1 - T/ T C β , with D = 1.08 ± 0.03 and β = 0.36 ± 0.03 over a large temperature range (1 > T/ T C > 0.4). Above the Curie temperature T C, an average quadrupole splitting value of about 0.44 mm/s is found. The temperature dependence of the isomer shift can be fitted within the harmonic approximation to a Debye model with a Debye temperature Θ D = 355.6 K.