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Asymptotic behavior of local dipolar fields in thin films

DOI: 10.1016/j.jmmm.2016.04.063 DOI Help

Authors: G. Bowden (University of Southampton) , G. B. G. Stenning (ISIS Facility) , G. Van Der Laan (Diamond Light Source)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Magnetism And Magnetic Materials

State: Published (Approved)
Published: August 2016

Abstract: A simple method, based on layer by layer direct summation, is used to determine the local dipolar fields in uniformly magnetized thin films. The results show that the dipolar constants converge ~1/m where the number of spins in a square film is given by (2m+1)^2. Dipolar field results for sc, bcc, fcc, and hexagonal lattices are presented and discussed. The results can be used to calculate local dipolar fields in films with either ferromagnetic, antiferromagnetic, spiral, exponential decay behavior, provided the magnetic order only changes normal to the film. Differences between the atomistic (local fields) and macroscopic fields (Maxwellian) are also examined. For the latter, the macro B-field inside the film is uniform and falls to zero sharply outside, in accord with Maxwell boundary conditions. In contrast, the local field for the atomistic point dipole model is highly non-linear inside and falls to zero at about three lattice spacing outside the film. Finally, it is argued that the continuum field B (used by the micromagnetic community) and the local field B_loc(r) (used by the FMR community) will lead to differing values for the overall demagnetization energy.

Journal Keywords: Micromagnetics, Dipolar fields, Internal magnetic fields

Subject Areas: Physics, Materials, Mathematics


Technical Areas: Accelerator Physics , Electrical Engineering , Insertion Devices , Magnets , RF , Theoretical Physics