Optically induced spin wave dynamics in [Co/Pd]8 antidot lattices with perpendicular magnetic anisotropy

Abstract

We present an all-optical time-resolved measurement of spin wave (SW) dynamics in a series of antidot lattices based on [Co(0.75 nm)/Pd(0.9 nm)]8 multilayer (ML) systems with perpendicular magnetic anisotropy. The spectra depend significantly on the areal density of the antidots. The observed SW modes are qualitatively reproduced by the plane wave method. The interesting results found in our measurements and calculations at small lattice constants can be attributed to the increase of areal density of the shells with modified magnetic properties probably due to distortion of the regular ML structure by the Ga ion bombardment and to increased coupling between localized modes. We propose and discuss the possible mechanisms for this coupling including exchange interaction, tunnelling, and dipolar interactions. We acknowledge the financial assistance from Department of Science and Technology Government of India under Grant No. SR/NM/NS-09/2011, S. N. Bose National Centre for Basic Sciences for Project No. SNB/AB/12-13/96, and NCN of Poland project DEC-2012/07/E/ST3/00538. S.P. acknowledges University Grants Commission for a senior research fellowship. The calculations presented in this paper were performed at the Poznan Supercomputing and Networking Center.