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.