Synthesis and magnetic property of cobalt hydroxide carbonate and cobalt oxide nanowires

Abstract

The present study is the first to report the successful synthesis of layered cobalt hydroxide carbonate nanowires templated by dodecyl sulfate assemblies by a homogeneous precipitation method using urea. The layered structure was composed of a cobalt hydroxide carbonate phase 1.9 nm thick and a dodecyl sulfate phase 2.3 nm thick. The width and length of the nanowires were tens of nm and greater than several micrometers, respectively. The layered cobalt hydroxide carbonate nanowires were transformed into Co₃O₄ and CoO nanowires by calcination in air and in vacuum, respectively, and were exfoliated to form ultrathin cobalt hydroxide carbonate nanowires approximately 3 nm wide. The present study also showed a dependence of the size and morphology on the magnetism of cobalt hydroxide carbonate. Although cobalt hydroxide carbonate nanorods synthesized in the presence of Na₂SO₄·10H₂O and lamellar-shaped cobalt compound templated by a mixture of C₁₆H₃₃OSO₃⁻ and C₁₈H₃₇OSO₃⁻ were antiferromagnetic materials, the layered cobalt hydroxide carbonate nanowires exhibited ferrimagnetism. This expression of ferrimagnetism was considered to be due to the formation of ultrathin cobalt hydroxide carbonate phases in the nanowires. Moreover, the Néel temperature of the obtained Co₃O₄ nanowires, which exhibited antiferromagnetism, was lower than that of commercially available Co₃O₄ particles.