Spin-wave modes in magnetic nanowires

Abstract

Spin-wave modes in magnetic transition-metal nanowires having diameters of about 10 nm and lengths on the order of 1 m are investigated by model calculations. There are quasicontinuous modes with k vectors parallel to the wires axis and discrete modes with k vectors perpendicular to the wire axis. Due to the small cross section of the wires, the perpendicular modes can be ignored in many cases and the low-temperature behavior of the wires is quasi one-dimensional. Using an analytic approach and exploiting the analogy between micromagnetism and quantum mechanics it is shown that all spin-wave modes with k vectors parallel to the wire axis are localized. The spin-wave localization is a micromagnetic analog to the Anderson localization of conduction electrons due to randomness in less than two dimensions, and, as in the electron analogy, arbitrarily small disorder is sufficient to cause the localization of all modes.

Finite-Temperature Micromagnetism

“…Consider a cubic soft region of volume in a very hard matrix. At zero temperature, the nucleation eigenmode (11) corresponds to a nucleation field . Note that (11) is valid for large and describes the hard-soft exchange in terms of clamped [26] boundary conditions.…”

“…This is a very natural approach, because the zero-temperature nucleation mode is the lowest-lying spin-wave mode [12]. In reality, it is necessary to account for the nonuniformity of the modes [11], [13]. Second, one can approach the problem from the viewpoint of "giant fluctuations" [9], [10].…”

“…First, spin waves are generally nonnegligible for small feature sizes, for example in nanowires [11]. This is a very natural approach, because the zero-temperature nucleation mode is the lowest-lying spin-wave mode [12].…”

Dipole-exchange spin excitations in a thin ferromagnetic nanoshell

“…Such excitations are a subject of research in magnonics [1] and spintronics [2]. In particular, spin excitations in nanoscale systems -thin ferromagnetic films [3][4][5], micron-sized magnetic quantum dots [6][7][8], nanowires [9][10][11] and other nanosystems -are studied intensively during recent years. In particular, spin-wave dispersion in nanosystems is an important area of experimental research.…”

Ferromagnetic resonance on Ni nanowire arrays

“…[23][24][25][26][27][28][29][30][31][32][33][34][35] The magnetic properties of Ni nanowires are controlled by the shape anisotropy, to which shape and magnetocrystalline contributions act as small perturbations. The main difference between the ideal nanowire and the real nanowire descriptions consists in the replacement of the cylinder-like symmetry with an ellipsoid of rotation symmetry.…”