Ground states of an array of magnetic dots with Ising-type anisotropy and subject to a normal magnetic field

Abstract

Dipole-dipole interactions in a square planar array of sub-micron magnetic disks (magnetic dots) have been studied theoretically. Under a normal magnetic field the ground-state of the array undergoes many structural transitions between the limiting chessboard antiferromagnetic state at zero field and the ferromagnet at a threshold field. At intermediate fields, numerous ferrimagnetic states having mean magnetic moments between zero and that of the ferromagnetic state are favorable energetically. The structures and energies of a selection of states are calculated and plotted, as are the fields required to optimally reverse the magnetic moment of a single dot within them. Approximate formulae for the dipolar energy and anhysteretic magnetization curve are presented.I.

Superferromagnetism on a two-dimensional array of magnetic nanodots: an Ising model approximation

“…This has been considered as an approximation. Nevertheless, nanodot systems where only interdot dipole interactions are relevant have been recently investigated in the literature being an important subject [34,35].…”

Boundary waves in ferromagnetically ordered two-dimensional arrays of magnetic dots

“…9 2014 BONDARENKO boundary (l x = 0), and B > 0 is a constant that describes the anisotropy of a separate particle with the easy axis perpendicular to the system plane. It is assumed that the magnetic moments of all particles in the ground state are parallel to each other and perpendicular to the plane of array, which takes place in a sufficiently strong field [6]. Note that this model is also applicable to description of an array of particles in a vortex state [6], representing cone state vortices in the presence of a magnetic field [7].…”

“…It is assumed that the magnetic moments of all particles in the ground state are parallel to each other and perpendicular to the plane of array, which takes place in a sufficiently strong field [6]. Note that this model is also applicable to description of an array of particles in a vortex state [6], representing cone state vortices in the presence of a magnetic field [7]. Linear oscillations of magnetization in this system are conveniently described using a canonical transfor mation of the classical quantities and (analo gous to the method of secondary quantization) for the classical amplitudes a l and : (2) Then, according to a procedure proposed in [8], we seek amplitude of some ηth eigenmode of the semi infinite array in the form of a linear combination of magnon operators of creation and annihilation at the lattice sites: …”

Collective magnon modes for magnetic dot arrays

“…The systems with Ising-type dipoles demonstrate a cascade of phase transitions under the variation of an external magnetic field [9]. The models [5][6][7] are discussed with regard to description of real spin systems, where the dipolar interaction is dominant.…”