Tunable magnetic anisotropy in two-dimensional arrays of Ni80Fe20elements

Abstract

Tunable two-fold magnetic anisotropy in two-dimensional arrays of Ni80Fe20 (permalloy) elliptical elements arranged along their long (LA) or short axis (SA) are demonstrated from the measurement of time-resolved magnetization dynamics. The anisotropy field is maximum (minimum) when the elements are closely packed along their LA (SA) and take an intermediate value when they are well separated. Micromagnetic simulations reveal that the centre mode of the ellipse shows the two-fold anisotropy and that the variation in the anisotropy field stems from the strong competition between the shape anisotropy of the constituent elements and the inter-element magnetostatic interaction fields within the arrays. The authors gratefully acknowledge the financial supports from the Department of Science and Technology, Government of India under Grant Nos. SR/NM/NS-53/2010 and SR/WOS-A/PS-27/2010, Department of Information Technology, Government of India under Grant No. 1(7)/2010/M&C, the Ministry of Education, Singapore and the SMF-NUS New Horizon Awards. S.S. acknowledges UGC, Government of India for senior research fellowship. The authors also acknowledge assistance from Dheeraj Kumar in calculating spin wave mode profiles.