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New magnetostatic modes in small nonellipsoidal magnetic particles
Author(s) -
Puszkarski H.,
Krawczyk M.,
Lévy J.C. S.
Publication year - 2006
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.200562447
Subject(s) - physics , amplitude , oscillation (cell signaling) , dipole , magnetic field , condensed matter physics , perpendicular , magnetization , field (mathematics) , plane (geometry) , optics , geometry , chemistry , quantum mechanics , biochemistry , mathematics , pure mathematics
Magnetostatic normal modes are investigated here in elongated rods. The dipolar field resulting from the dipole–dipole interactions is calculated numerically in points of the axis connecting opposite rod face centers ( central axis ) by collecting individual contributions to this field coming from each of the atomic planes perpendicular to the central axis. The applied magnetic field is assumed to be oriented along the central axis, and the magnetization to be uniform throughout the sample. The frequency spectrum of magnetostatic waves propagating in the direction of the applied field is found numerically by solving the Landau–Lifshitz equation of motion with the spatially nonhomogeneous dipolar field taken into account; the mode amplitude profiles are depicted as well. While energetically highest modes have bulk‐extended character, the modes forming the lower part of the spectrum are localized in the subsurface region ( bulk‐dead modes ). Between these two mode types, magnetostatic modes of a new type ( comb modes ) are found to occur, characterized by two clearly discernible regions: a zone of fast amplitude oscillations inside the rod, and narrow slow‐oscillation regions at the borders. Absorbing virtually no energy from an applied alternating field, comb modes will have no significant contribution to the magnetic noise. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)