Study of the Internal Fields Acting on Iron Nuclei in Iron Garnets, Using the Recoil-Free Absorption in Fe57 of the 14.4-kev Gamma Radiation from Fe57m

Abstract

The shape of the recoil-free absorption spectrum obtained in iron garnet absorbers has been investigated, using, as a source, a ${\mathrm{Co}}^{57}$ source embedded in stainless steel. The results confirm the existence of two iron sublattices each showing a Zeeman structure characterized by different parameters. No significant differences have been detected between the Zeeman structure in yttrium iron garnet and dysprosium iron garnet. The values obtained for the effective magnetic field at the ${\mathrm{Fe}}^{57}$ nuclei at room temperature are 3.90×${10}^5$ oe and 4.85×${10}^5$ oe for the $d$ and $a$ iron lattice sites, respectively. At liquid air temperature the corresponding fields are 4.6×${10}^5$ oe and 5.4×${10}^5$ oe, respectively. The mean value of the chemical shift for the $d$ sites relative to stainless steel is about 0.04±0.005 cm/sec and about 0.06±0.005 cm/sec for the $a$ sites.