Sign determination of the hyperfine field by elliptically polarized Moessbauer source

A novel approach of determining the sign of the hyperfine magnetic field using elliptically polarized resonant γ-photons is presented. The method is demonstrated by a transmission experiment on α-Fe using a 57Co:α-Fe source partially saturated parallel and antiparallel to each other in plane at a shallow angle of ∼10o relative to the k-vector of the γ-rays. The evaluation procedure decomposes the resulting spectra into four linearly independent principal subspectra, namely I|| , Iperpendicular, I↑↑, I↑↓, the linearly polarized parallel and perpendicular as well as the circularly polarized parallel and antiparallel components, respectively, and derives the experimental average polar angles of the hyperfine fields both in the source and absorber α-Fe foils as well as the mean difference of the azimuth angles. By this procedure not only the relative alignment but also the relative sign is determined.