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Magnetic dipolar interaction in ultrathin films: Structural and size effects

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Title: Magnetic dipolar interaction in ultrathin films: Structural and size effects
Authors: Leon, H. hleon@imre.oc.uh.cu, Estevez-Rams, E.1
Source: Journal of Magnetism & Magnetic Materials. Jul2009, Vol. 321 Issue 14, p2150-2159. 10p.
Subjects: Dipole moments, Magnetic properties of thin films, Size effects in thin films, Magnetic dipoles, Atomic structure, Layer structure (Solids), Thickness measurement
Abstract: Abstract: A previously introduced formalism for calculating magnetic dipolar anisotropy energy in atomic layered structures is further developed. Numerical results are presented for ultrathin films with different close-packed (face centered cubic (FCC) [111]) and non-close-packed (FCC [001] and body centered cubic (BCC) [001]) structures. Structural effects become apparent in the magnetocrystalline dipolar anisotropy energy when the ratio between the interlayer separation c and the 2D lattice constant a is changed. Despite the long-range character of the dipolar interaction, it is shown that the number of significantly interacting layers, conventially called coupled layers, is limited and depends on the structural aspect ratio . The slope in the observed linear dependence between and the inverse of the film thickness t is explained by the number of the so-called coupled layers, and not by a surface contribution to volume values. Size effects appearing in are unambiguously distinguished from structural effects. Effective anisotropy energy and are presented for Co [0001] and Ni [001] ultrathin films. It is verified that the dipolar interaction makes an important contribution to , but the spin reorientation transition is determined by non-dipolar interactions. The former favors the magnetization switching only when the size aspect ratio , with d the characteristic lateral dimension of the film, is sufficiently small. Applications to other layered arrays of magnetic dipoles are straightforward. [Copyright &y& Elsevier]
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Database: Engineering Source
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Abstract:Abstract: A previously introduced formalism for calculating magnetic dipolar anisotropy energy in atomic layered structures is further developed. Numerical results are presented for ultrathin films with different close-packed (face centered cubic (FCC) [111]) and non-close-packed (FCC [001] and body centered cubic (BCC) [001]) structures. Structural effects become apparent in the magnetocrystalline dipolar anisotropy energy when the ratio between the interlayer separation c and the 2D lattice constant a is changed. Despite the long-range character of the dipolar interaction, it is shown that the number of significantly interacting layers, conventially called coupled layers, is limited and depends on the structural aspect ratio . The slope in the observed linear dependence between and the inverse of the film thickness t is explained by the number of the so-called coupled layers, and not by a surface contribution to volume values. Size effects appearing in are unambiguously distinguished from structural effects. Effective anisotropy energy and are presented for Co [0001] and Ni [001] ultrathin films. It is verified that the dipolar interaction makes an important contribution to , but the spin reorientation transition is determined by non-dipolar interactions. The former favors the magnetization switching only when the size aspect ratio , with d the characteristic lateral dimension of the film, is sufficiently small. Applications to other layered arrays of magnetic dipoles are straightforward. [Copyright &y& Elsevier]
ISSN:03048853
DOI:10.1016/j.jmmm.2009.01.009