Temperature Dependence of Magnetic Domain Structure and Wall Energy in Single-Crystal Thulium Orthoferrite

Abstract

A study has been made of the temperature and field dependence of the magnetic domain structure in thin single‐crystal c‐axis plates of thulium orthoferrite from room temperature down through the reorientation range (80° to 94°K) where the net magnetization moves from the c axis to the a axis. Visual observation of the domain pattern was achieved by means of Faraday rotation. In the reorientation range the domain pattern consists of stripes bounded by Néel walls parallel to the b axis. A field applied along the c axis causes unconnected domains to collapse into cylindrical domains which are stable within a range of field of about 7 Oe at room temperature and increasing to nearly 20 Oe at the upper end of the reorientation range. Cylindrical domains with diameters as small as 7 μ or 16% of the sample thickness have been observed. The temperature dependence of the domain‐wall energy, which decreases by a factor of five from room temperature down to 94°K and faster still in the reorientation range, is deduced from measurements of domain width.