DEPENDENCE OF NUCLEAR POLARIZED FE57 MOSSBAUER SPECTRA ON MAGNITUDE AND SIGN OF HYPERFINE FIELD

The Mössbauer spectra of Fe57, with the Co57 source in iron and palladium matrices, respectively, have been measured in a He3/He4 dilution refrigerator. Both the magnitude and sign of the effective field at Co57 can be determined from nuclear polarization effects in the spectra, without recourse to an external magnetic field. Experimental data are also presented on the Kapitza thermal boundary resistance which, together with radioactive self-heating, prevents the source from cooling below 0.15°K. © 1969 The American Physical Society.