X‐Ray Diffraction Contrast on Ferromagnetic Domain Walls in Fe‐Si Single Crystals

Abstract

The contrast of ferromagnetic domains in (001) Fe-304 Si single crystal plates is studied using X-ray diffraction topography. This contrast is found to be due solely to the difference in deformation on opposite sides of the wall which is produced by magnetostriction. 180' walls are therefore never visible, whereas 90' walls show contrast if diffracting planes not belonging to the zone m,nil are used (m, and m, are unit vectors parallel t o the magnetization on the two sides of the wall). Der Kontrast von ferromagnetischen Domiinen in (001) F e 3 % Si Einkristallpliittchen wird mit der rontgentopographischen Methode untersucht. Der Kontrast hiingt einzig von dem durch Magnetostriktion eneugten Deformationsunterschied auf beiden Seiten der Wand ab. 180O-Wiinde sind deswegen immer unsichtbar, wiihrend 90O-Wiinde nur d a m einen Kontrast aufmeisen, wenn die benutzten Streuungsebenen nicht zur Zone m, -mi1 gehoren (m, und m, sind Einheitavektoren in Richtung der Magnetisierungen auf beiden Seiten der Wand).

Decomposed bloch walls in iron

“…Consequently, the zig-zag wall must be invisible. This result is in agreement with the extinction rule of Polcarova et al [18].…”

“…As Polcarova and Kaczer [18] first pointed out, the contrast of magnetic walls is mainly due to magnetostriction. Assuming a flat 90° wall : (110) plane which is a coherent twinning boundary between two adjacent domains (I, II) freely deformed by magnetostriction, they showed that for a diffraction vector g so that (MI -M1J.…”

Two- and Three-Beam X-ray Diffraction Imaging of Domains in Magnetite

“…The accepted view is that whatever contrast is observed is due to the slight difference in distortion of the various domains (Polcarova  & Kacze  r, 1967;Polcarova  & Gemperlova  , 1969;Schlenker et al, 1968). This difference is associated with the symmetry lowering, which in turn is related to the presence of spontaneous magnetization along the h111i directions in the ferrimagnetic phase of magnetite.…”

Study of magnetostrictive deformation of Fe–Si by X-rays

“…A line focus X-ray tube with Mo anode was used. The beam reflected from the first crystal was limited by slits so as to irradiate a subgrain in the schcxond crystal having a low dislocation density and containing 90" walls fulfilling the visibility rule for the reflection used [2]. The second crystal was rotated thi*ough the reflecting position and the intensity of the reflected beam was measured by a scintillation counter.…”

“…The origin of the contrast has been explained on the basis of the magnetostrictive deformation of the crystal [l]. Due to this deformation the crystal lattice of iron is slightly tetragonal and a 90" wall lying in the (110) plane can be considered as a coberent twin boundary [2]. When crossing this wall, some lattice planes change their distance and orientation.…”