Magnetization of magnetic films determined with Larmor pseudo-precession and spin echo

The effect of Larmor pseudo-precession (LPP) occurs at reflection of polarized neutrons from a magnetic film [B.P. Toperverg, et al. Physica B 356 (2005) 1] magnetized at an angle with respect to the incident polarization vector direction. The neutron wave spin components transmitted into the film are split due to the Zeeman effect and reflected differently from other interface of the film or by the substrate. The interference outside the sample between the different spin components of reflected wave results in an effective rotation of the neutron polarization around the film magnetization direction. The angle of effective rotation or LPP as a function of the incoming angle depends on the parameter set of the film, e.g. the layer magnetization distribution. This effect was studied with a ∼100-nm-thick ⁵⁷Fe film on sapphire substrate in the remanent state. The Fe-film magnetization was determined by the spin rotation in the total reflecting region. These polarization rotations are verified with the spin-echo spectrometer (IN3+ZETA at ILL, Grenoble).