The effect of high external magnetic fields on the hyperfine interactions in the Fe-Ni phases of the Santa Catharina meteorite

A thin slice of the Santa Catharina meteorite has been measured at 4.2 K in applied fields of 20, 40, 60, 90, and 120 kOe. The spectra were fitted adequately with a superposition of five quadruplets. Two of these are attributed to Fe72Ni28 with effective fields, suggesting that part of that phase is ferromagnetically ordered and part is paramagnetic. Two other components arise from crystallographically ordered FeNi, with the EFG principal axis parallel and perpendicular, respectively, to the effective field. The fifth subspectrum is due to unordered FeNi. The ordering in the FeNi phases is ferromagnetic and the magnitude of the effective fields can be explained in terms of dipolar and demagnetizing fields.