Effect of a randomly oriented field on superparamagnetic ultrafine particles

• Published in: Thin solid films Vol. 518; no. 21; pp. 6087 - 6092
• Main Authors: Housni, A., Labzour, A., Sayouri, S., Elmesbahi, A., Limame, K.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 31.08.2010; Elsevier
• Subjects: Assembly; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Eigenvalues; Exact sciences and technology; Ferromagnetic relaxation; Ferromagnetism; Fokker-Planck equation; Magnetic fields; Magnetic properties and materials; Magnetic properties of monolayers and thin films; Magnetic properties of surface, thin films and multilayers; Mathematical analysis; Physics; Saturation (magnetic); Superparamagnetic; Thin films; Ultrafine particles; Ultrafine particles; Superparamagnetic; Fokker–Planck equation; Ferromagnetic relaxation; Relaxation; Anisotropy; Ferromagnetic materials; Eigenvalues; Ultrafine particle; Fokker-Planck equation; Relaxation time; Saturation magnetization
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2010.05.119

The effect of a constant and a randomly oriented magnetic field H(ψ, ϕ), on the Néel relaxation time τ, of an assembly of ultrafine ferromagnetic particles with uniaxial anisotropy, is investigated. In this regard, the smallest non-vanishing eigenvalue of the Fokker–Planck equation is calculated as a function of ψ, ϕ and the parameter h = M svH / k BT, where M s and v are denoting the saturation magnetization and the volume of a particle, respectively. The results obtained bring noticeable changes compared to previous calculations, and give satisfactory interpretation of the relaxation phenomenon in such systems.