Collective modes for an array of magnetic dots with perpendicular magnetization

Abstract

The dispersion relations of collective oscillations of the magnetic moment of magnetic dots arranged in square-planar arrays and having magnetic moments perpendicular to the array plane are calculated. The presence of the external magnetic field perpendicular to the plane of array, as well as the uniaxial anisotropy for single dot are taken into account. The ferromagnetic state with all the magnetic moments parallel, and chessboard antiferromagnetic state are considered. The dispersion relation yields information about the stability of different states of the array. There is a critical magnetic field below which the ferromagnetic state is unstable. The antiferromagnetic state is stable for small enough magnetic fields. The dispersion relation is non-analytic as the value of the wave vector approaches zero. Non-trivial Van Hove anomalies are also found for both ferromagnetic and antiferromagnetic states.

Theoretical formalism for collective spin-wave edge excitations in arrays of dipolarly interacting magnetic nanodots

“…The block-matrix Ω ′ ij is the projection of the block-matrixΩ ij in the same sense as presented by equation (14).…”

“…Such a state of the static magnetization, shown in Fig. 10 and having a zero net magnetic moment, is, usually, naturally formed during the demagnetization and is called the chessboard AFM (CAFM) state 14,17 . In reality, however, demagnetization does not lead to an ideal CAFM state 18 , but, instead, it leads to the formation of clusters with local periodicity due to the spontaneous symmetry breaking between the two equivalent ground states of the array.…”

“…One of the examples of such self-biased artificial magnetic materials are the arrays of periodically arranged and dipolarly coupled anisotropic magnetic nanoelements, in which the nano-size of the element guarantees its monodomain state, while the shape or/and crystallographic anisotropy determines the definite direction of its static magnetization [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] . The static magnetization of each anisotropic nanoelement can have more than one stable direction, which means that an array can exist in several distinct meta-stable static magnetization states 14,21 . Obviously, the static magnetization state of an array strongly affects the array's dynamic magnetization properties, such as the spectrum of its spin wave excitations and characteristics of the array's interaction with external electromagnetic waves 17,19,23 .…”

Discrete breathers in an one-dimensional array of magnetic dots

“…The artificially manufactured periodic arrays of magnetic particles have received much attention in the literature during the last two decades [1][2][3][4][5][6][7][8]. Apart from their technological importance as candidates for the highdensity magnetic storage media [1,2,5], these arrays appear to be a good testing ground for studying various nonlinear magnetic wave phenomena [9][10][11].…”

Magnetization processes in rectangular versus rhombic planar superlattices of magnetic bars

“…[1][2][3][4][5][6][7][8][9] Fundamental interest is motivated by the possibility to controllably form nontrivial collective magnetic states 10 and manipulate phase transitions 11,12 between them, controlled either by the material and shape parameters of nanoelements and by the geometric parameters of artificial superstructures. Such superstructures for prospective applications in spintronics and nanotechnologies are mainly studied in the simplest geometry of a square superlattice, having high enough symmetry [13][14][15] which can hide however certain important manifestations of magnetic interactions.…”