Uniaxial polarization analysis of bulk ferromagnets: theory and first experimental results

Malyeyev, A.; Titov, I.; Dewhurst, C.; Suzuki, K.; Honecker, D.; Michels, A.

doi:10.1107/S1600576722003508

Figure 1
Sketch of the SANS setup and of the two most often employed scattering geometries in magnetic SANS experiments. (a) Applied magnetic field $[{\bf H}_{0}]$ perpendicular to the incident neutron beam ( $[{\bf k}_{0}\perp{\bf H}_{0}]$ ); (b) $[{\bf k}_{0}\parallel{\bf H}_{0}]$ . The momentum-transfer or scattering vector $[{\bf q}]$ corresponds to the difference between the wavevectors of the incident ( $[{\bf k}_{0}]$ ) and the scattered ( $[{\bf k}_{1}]$ ) neutrons, i.e. $[{\bf q} = {\bf k}_{0}-{\bf k}_{1}]$ . Its magnitude for elastic scattering, $[q = |{\bf q}| = (4\pi/\lambda)\sin(\psi)]$ , depends on the mean wavelength λ of the neutrons and on the scattering angle $[2\psi]$ . For a given λ, sample-to-detector distance $[L_{{\rm SD}}]$ and distance $[r_{{\rm D}}]$ from the centre of the direct beam to a certain pixel element on the detector, the q value can be obtained using $[q\cong k_{0}({r_{{\rm D}}} / {L_{{\rm SD}}})]$ . The symbols `P', `F' and `A' denote, respectively, the polarizer, spin flipper and analyzer, which are optional neutron optical devices. Note that a second flipper after the sample has been omitted here. In spin-resolved SANS (POLARIS) using a ³He spin filter, the transmission (polarization) direction of the analyzer can be switched by 180° by means of a radiofrequency pulse. SANS is usually implemented as elastic scattering ( $[k_{0} = k_{1} = 2\pi/\lambda]$ ), and the component of $[{\bf q}]$ along the incident neutron beam [i.e. q_x=0 in (a) and q_z=0 in (b)] is neglected. The angle θ may be conveniently used in order to describe the angular anisotropy of the recorded scattering pattern on a two-dimensional position-sensitive detector. Image taken from Michels (2021

), reproduced by permission of Oxford University Press.

JOURNAL OF
APPLIED
CRYSTALLOGRAPHY

ISSN: 1600-5767

Volume 55| Part 3| June 2022| Pages 569-585

https://doi.org/10.1107/S1600576722003508

Open

access

Search IUCr Journals		doi		Advanced search
Author		volume	page