Application of Mossbauer spectroscopy in magnetism

An overview is provided on our recent work that applies Fe-57 Mossbauer spectroscopy to specific problems in nanomagnetism. Fe-57 conversion electron Mossbauer spectroscopy (CEMS) in conjunction with the Fe-57 probe layer technique as well as Fe-57 nuclear resonant scattering (NRS) were employed for the study of various nanoscale layered systems: (i) metastable fct-Fe; a strongly enhanced hyperfine magnetic field B-hf of similar to 39 T at 25 K was observed in ultrahigh vacuum (UHV) on uncoated three-monolayers thick epitaxial face-centered tetragonal (fct) Fe-57(110) ultrathin films grown by molecular-beam epitaxy (MBE) on vicinal Pd(110) substrates; this indicates the presence of enhanced Fe local moments, mu(Fe), as predicted theoretically; (ii) Fe spin structure; by applying magnetic fields, the Fe spin structure during magnetization reversal in layered (Sm-Co)/Fe exchange spring magnets and in exchange-biased Fe/MnF2 bilayers was proven to be non-collinear and depth-dependent; (iii) ferromagnet/semiconductor interfaces for electrical spin injection; CEMS was used as a diagnostic tool for the investigation of magnetism at the buried interface of Fe electrical contacts on the clean surface of GaAs(001) and GaAs(001)-based spin light-emitting diodes (spin LED) with in-plane or out-of-plane Fe spin orientation; the measured rather large average hyperfine field of similar to 27 T at 295 K and the distribution of hyperfine magnetic fields, P(B-hf), provide evidence for the absence of magnetically "dead" layers and the existence of relatively large Fe moments (mu(Fe) similar to 1.8 mu(B)) at the ferromagnet/semiconductor interface. - Finally, a short outlook is given for potential applications of Mossbauer spectroscopy on topical subjects of nanomagnetism/spintronics.