Order-Disorder Transitions in Iron-Nickel (50%-50%) Alloys from Iron Meteorites as Studied by Mössbauer Spectroscopy

Iron meteorites contain an ordered FeNi (50%-50%) alloy. By study of the disordering process above the transition temperature $T_c\simeq 593$ K with Mössbauer spectroscopy, it is shown that the hyperfine parameters reflect the degree of order. This depends on the cooling rate of the meteorites. As the hyperfine parameters, and therefore the degree of order, vary from meteorite to meteorite, the ordered FeNi alloy contains information on the relative cooling rates of meteorites.