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Origin of four-fold anisotropy in square lattices of circular ferromagnetic dots

G. N. Kakazei·Yu. G. Pogorelov·M. D. Costa·T. Mewes·P. E. Wigen·P. C. Hammel·V. O. Golub·T. Okuno·V. Novosad
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Abstract

We discuss the four-fold anisotropy of in-plane ferromagnetic resonance (FMR) field $H_r$, found in a square lattice of circular Permalloy dots when the interdot distance $a$ gets comparable to the dot diameter $d$. The minimum $H_r$, along the lattice $<11>$ axes, and the maximum, along the $<10>$ axes, differ by $\sim$ 50 Oe at $a/d$ = 1.1. This anisotropy, not expected in uniformly magnetized dots, is explained by a non-uniform magnetization $\bm(\br)$ in a dot in response to dipolar forces in the patterned magnetic structure. It is well described by an iterative solution of a continuous variational procedure.

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G. N. Kakazei, Yu. G. Pogorelov, M. D. Costa, T. Mewes, P. E. Wigen, P. C. Hammel, V. O. Golub, T. Okuno, V. Novosad. 2006-06-13. Origin of four-fold anisotropy in square lattices of circular ferromagnetic dots. https://doi.org/10.1103/physrevb.74.060406

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