Magnetic Properties of Ferromagnetic Cobalt Grown in an Applied Magnetic Field

Preparation of cobalt crystals from a melt requires temperatures above its Curie temperature, T_C = 1394 K, meaning the nucleation and growth will occur in the paramagnetic state. In this work, a sulfur flux was used and the liquidus was shifted as low as 1150 K [1], thereby allowing crystal formation in the ferromagnetic phase. A magnetic field, B_syn = 0, 3 T, or 9 T, was applied during synthesis, and the resulting polycrystalline samples were characterized with XRD and magnetometry, which provided magnetization data, M(5 K ≤ T ≤ 300 K, B = 10 mT) and M(T = 5 K or 300 K, −1 T ≤ B ≤ 7 T), with B oriented parallel and perpendicular to the growth axis which was along B_syn. Overall, our data are consistent with magnetism reported for single crystals [2,3]. However, the remnant magnetization was found to increase with the magnitude of B_syn, while trends in other magnetic properties, such as the maximum value of magnetization and the coercive field, were not as clearly established. Our results demonstrate using a sulfur flux allows for nucleation and growth of cobalt crystals below T_C while preserving known magnetic properties.

[1] X. Lin, S.L. Bud’ko, P.C. Canfield, Philos. Mag. 92 (2012) 2436, doi:10.1080/14786435.2012.671552.

[2] S. Kaya, Sci. Rep. Tohoku Univ. 17 (1928) 1157.

[3] K. Honda, M. Masumoto, Sci. Rep. Tohoku Univ. 20 (1931) 323.