Néel walls and line transitions in a (100) garnet film

Abstract

An investigation was made of novel domain wall structures in (100) SmTmCaGe garnet films. These (100) oriented films have strong in-plane anisotropy resulting in the formation of Néel type domain walls in spite of the large thickness (∼1 μm) of the films. The dipolar nature of these walls was detected by use of a modified Bitter technique in which a bias field polarized the magnetic particles perpendicular to the film plane. Line transitions separating antiparallel domain wall segments were observed to move along the walls when appropriate polarity in-plane fields were applied. These line transitions are analogous to the Bloch point and crosstie observed in NiFe films. In the garnet films, however, anisotropy is stronger, and because the magnetization is much weaker, the crosstie does not form. Theoretical considerations suggest that the Néel wall has a width of about 1500 Å and that alternate line transitions, having different magnetization configurations, are nearly identical in width (∼600 Å) and energy. Furthermore, since the magnetization is low, there is little interaction between line transitions and they may be relatively densely packed along the Néel wall.

Magnetic Vortex Dynamics Using the Optical Cotton-Mouton Effect

“…The fact that a Neel wall (with M in the film plane) has lower energy than a Bloch wall (with M in the wall plane) was already discussed in connection with a garnet film having properties very similar to ours. 6 Magnetocrystalline anisotropy (K\ = -6 x 10 3 erg/cm 3 ) produces easy directions of magnetization along [110] axes. The four [110] domains in Fig.…”

Domain Wall Tip for Manipulation of Magnetic Particles

“…We assume that the magnetic moment of the tip is related to the magnetization M s (M s 10 5 A=m) of the garnet film by m d 4=3w 3 M s . Here w is the domain wall width at the tip, which we estimate to be w 300 nm [15,16]. The tip is here taken as a spherical particle of radius w, which is expected to be reasonable approximation, except at very small distances where the actual geometry of the tip should be accounted for in more detail.…”