Configurational anisotropic spin waves in cross-shaped Ni80Fe20 nanoelements

Abstract

Optically induced spin waves in Ni80Fe20 (permalloy) cross-shaped nanoelements are studied by time-resolved magneto-optical Kerr effect microscope. A strong anisotropy in the spin wave modes are observed with the orientation angle (ϕ) of the in-plane bias magnetic field. As ϕ deviates from 0° a single resonant mode splits into a numbers of modes, while the powers of the higher frequency modes increase as ϕ increases from 0 to 45°. The lowest frequency mode shows a four-fold configurational anisotropy. The mode of a single cross remains unaffected by the magnetostatic interaction of the neighbouring elements for ϕ = 0°, while the effect increases with ϕ and becomes maximum at 45°, making these elements interesting candidates as building blocks for magnonic devices. 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, INT/EC/CMS (24/233552), INT/JP/JST/P-23/09, and SR/WOS-A/PS-27/2010, Department of Information Technology, Government of India under Grant No. 1(7)/2010/M&C, and Japan Science and Technology Agency Strategic International Cooperative Program under Grant No. 09158876. B.K.M. and D.K. acknowledge CSIR and B.R. acknowledges UGC, Government of India for senior research fellowships.