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.