Annealing-Induced Mobility Changes in Rare-Earth Orthoferrite

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 Sm0.55Tb0.45FeO3, 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.