Polarization of Nuclear Resonance Radiation in FerromagneticFe57

Abstract

The ferromagnetic property of iron has made possible a simple measurement of the polarization of resonance radiation from the level in Fe 57 at 14 kev and a direct observation of a strong correlation in direction between the magnetization in a ferromagnetic domain and the internal magnetic field at the nucleus. Recent observations have shown 1 " 4 that the 14-kev radiation undergoes a strong absorption of the Mossbauer type 5 at room temperature and that the absorption spectrum displays 2 a hyperfine structure corresponding to the splitting of the 14-kev level by the internal field. The present experiment consists in observing the resonant absorption with a ferromagnetic source and absorber magnetized parallel or perpendicular to each other.The apparatus is shown schematically in Fig. 1. On one side of the alnico magnet M is fastened the yoke structure designated by F. The pole pieces P bridge the circular gap formed by the yoke, and the source S is mounted in the gap between the pole pieces. An identical structure for providing a magnetic field in the absorber A is mounted on the other side of the same magnet M. The design allows the pole pieces P and P' (shown also in side view in Fig. 1) to be rotated relative to each other so that the relative orien-

Sign determination of the hyperfine field by elliptically polarized Mössbauer source

“…Mössbauer-spectroscopy (MS) is exquisite tool to determine the magnetization direction of buried layers using a conventional Mössbauer source, the scattering amplitude being dependent on the angle of the wave vector k and the hyperfine (hf) field, H hf . Using linearly polarized radiation, the alignment may [1,2], but the sign of the magnetization can obviously not be retrieved. The sign of the k-parallel component of the magnetization can be determined using circularly polarized [3][4][5] Scheme of the experimental setup and the corresponding polar coordinates of the local (hyperfine) and the laboratory systems of source and absorber.…”

Electron proportional gas counter for linear and elliptical Mössbauer polarimetry

“…Nevertheless, the alignment of H hf also influences the polarization of the resonance lines, a fact opening the way to the determination of the alignment of the k-perpendicular component of M. Indeed, linearly polarized radiation allows retrieving the k-perpendicular alignment of M. 4 Mössbauer polarimetric experiments were suggested and demonstrated in transmission geometry soon after the discovery of the Mössbauer effect, using a magnetized ferromagnetic 57 Co͑␣-Fe͒ source by recording the amplitude of a single resonance line at zero velocity 4 and, somewhat later, also by recording the full Mössbauer spectrum. 5 The method was applied to determining the magnetization alignment of a uniaxial antiferromagnet by Gonser et al 6 and by Grant et al 7 It took almost four decades to demonstrate the feasibility of linear Mössbauer polarimetry for thin films in a CEMS chamber and to apply the method for studying the bulk-spin-flop transition of an antiferromagnetically coupled Fe/Cr multilayer in a linear CEMS polarimeter.…”

“…8 Linearly polarized radiation is obviously not suitable to determine the direction of the magnetization. 4 Nonetheless, the sign of the k-parallel component of the magnetization can be determined using circularly or elliptically polarized radiation. [9][10][11][12][13][14][15] Determination of the alignment of the magnetization of a homogeneously magnetized ͑e.g., 57 Fe-containing͒ ferromagnetic specimen via the spectrum pattern is a textbook case in MS in the thin-emitter/thin-absorber limit.…”

Nuclear Resonant Magnetometry and its Application toFe/CrMultilayers

“…The American Physical Society 037201-1 of the magnetization vectorM M [12]. For example, for iron the 57 Fe hyperfine field is oriented antiparallel to the magnetization vector [13], and has a value of ÿ33:0 T at room temperature [14].…”