Anti-Invar properties and magnetic order in fcc Fe-Ni-C alloy

作者：Nadutov V M^*; Kosintsev S G; Svystunov Ye O; Garamus V M; Willumeit R; Eckerlebe H; Ericsson T; Annersten H

来源：Journal of Magnetism and Magnetic Materials, 2011, 323(22): 2786-2791.

DOI：10.1016/j.jmmm.2011.05.053

• Fe-Ni-C anti-Invar
• Thermal expansion
• Mossbauer effect
• SANS

Anti-Invar effect was revealed in the fcc Fe-25.3%Ni-0.73%C (wt%) alloy, which demonstrates high values of thermal expansion coefficient (TEC) (15-21) x 10(-6) K-1 accompanied by almost temperature-insensitive behavior in temperature range of 122-525 K. Alloying with carbon considerably expanded the low temperature range of anti-Invar behavior in fcc Fe-Ni-based alloy. The Curie temperature of the alloy T-C = 195 K was determined on measurements of temperature dependences of magnetic susceptibility and saturation magnetization. The Mossbauer and small-angle neutron scattering (SANS) experiments on the fcc Fe-25.3%Ni-(0.73-0.78)%C alloys with the varying temperatures below and above the Curie point and in external magnetic field of 1.5-5 T were conducted. Low value of the Debye temperature Theta(D) = 180 K was estimated using the temperature dependence of the integral intensity of Mossbauer spectra for specified temperature range. The inequality B-eff = (0.7-0.9)B-ext was obtained in external field Mossbauer measurement that points to antiferromagnetically coupled Fe atoms, which have a tendency to align their spins perpendicular to B-ext. Nano length scale magnetic in homogeneities nearby and far above T-C were revealed, which assumed that it is caused by mixed antiferromagnetically and ferromagnetically coupled Fe atom spins. The anti-Invar behavior of Fe-Ni-C alloy is explained in terms of evolution of magnetic order with changing temperature resulting from thermally varied interspin interaction and decreasing stiffness of interatomic bond.

• 出版日期2011-11