Der Einfluß magnetischer Felder auf die Torsionsscherung von MBBA / Torsional Shear Flow of MBBA in Magnetic Fields

Abstract

Quantitative results are reported on the influence of a homogeneous magnetic field upon the torsional shear flow of a homeotropic layer at 22.5 °C. In subcritical fields H_x parallel to the layer, as well as in weak fields H_z normal to the layer, one gets K₃/μ₀ X_a = 3.76±0.2 A² . In oblique magnetic fields (H_x , 0, H_z) one obtains (λ₂-λ₁)/μ₀ X_a=(11.7±0.4)x10¹⁰ A² m^-2 s. In addition, a hysteresis effect in supercritical fields H_x and the formation of a long and straight magnetic wall are described. The magnetic wall becomes distorted under the action of the shear flow. Hereby a new domain can be produced which has a 180° inversion wall parallel to the boundaries of the layer.