Mössbauer and magnetic study of the antiferro to ferrimagnetic phase transition in Fe9S10 and the magnetokinetics of the diffusion of iron atoms during the transition

Abstract

The antiferromagnetic to ferrimagnetic phase transition referred to as the λ transition in Fe9S10 has been explained by many workers on the basis of a structural change without any experimental evidence. Our Mössbauer and X-ray diffraction results support Lotgering’s suggestion that the ferrimagnetism at about 493 K arises from the 4C superstructure. The antiferromagnetic to ferrimagnetic (λ) phase transition is explained in terms of a vancancy rearrangement. Using absolute reaction rate theory and measurements of magnetization as a function of time at constant temperature around the transition, coefficients of diffusion for iron atoms along the C axis have been determined over the range 440 to 484 K and found to be 10−18 cm2/sec.