Annealing-Induced Mobility Changes in Rare-Earth Orthoferrite

Abstract

The domain‐wall mobility at room temperature, as measured in thin crystal platelets of flux‐grown rare‐earth orthoferrites, has been found to depend strongly on annealing treatment. Increases of 30% above the as‐grown mobility have been achieved by anneals in the 1200–1300°C range, but further annealing at higher temperatures causes the mobility to decrease substantially. For samples of flux‐grown YFeO₃ and Sm_0.55Tb_0.45FeO₃, peak values of 6500 and 1440 cm sec⁻¹ Oe⁻¹ were attained, respectively, which are higher than any previously published value. Samples of Bridgman‐grown YFeO₃ were also studied. These samples showed no large increases in mobility; however, a region of abnormally low mobility was observed to increase in value, rising to that of the remainder of the material, ∼5500 cm sec⁻¹ Oe⁻¹, after annealing at 1300°C. This controlled annealing therefore makes possible improvements in domain‐wall mobility and removal of variation in mobility from sample to sample.