Magnetic features of some extraterrestrial Fe-Ni-Co alloys: Study using magnetization measurements and Mössbauer spectroscopy

Magnetic features of extraterrestrial Fe-Ni-Co alloys from iron and stony-iron meteorites were studied by scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), X-ray diffraction, Mössbauer spectroscopy and magnetization measurements. SEM with EDS demonstrated the presence of different compositions of the α-Fe(Ni, Co), α₂-Fe(Ni, Co), γ-Fe(Ni, Co) and γ-FeNi(Co) phases in various alloys with variations in Ni concentrations. The Mössbauer spectra of Fe-Ni-Co alloys consist of different numbers of magnetic sextets. The values of ⁵⁷Fe hyperfine parameters were assigned to corresponding α-Fe(Ni, Co), α₂-Fe(Ni, Co), γ-Fe(Ni, Co) and γ-FeNi(Co) phases. The saturation magnetic moments for some Fe-Ni-Co alloys were slightly higher while those for other Fe-Ni-Co alloys were slightly lower than that of pure Fe. The zero-field-cooled (ZFC) and field-cooled (FC) branches of the magnetization curves showed unusual behavior for Fe-Ni-Co alloys from three meteorites when the ZFC curve lies over the FC one which is a very rare phenomenon.