Programmability of Co-antidot lattices of optimized geometry

Abstract

Programmability of stable magnetization configurations in a magnetic device is a highly desirable feature for a variety of applications, such as in magneto-transport and spin-wave logic. Periodic systems such as antidot lattices may exhibit programmability; however, to achieve multiple stable magnetization configurations the lattice geometry must be optimized. We consider the magnetization states in Co-antidot lattices of ≈50 nm thickness and ≈150 nm inter-antidot distance. Micromagnetic simulations were applied to investigate the magnetization states around individual antidots during the reversal process. The reversal processes predicted by micromagnetics were confirmed by experimental observations. Magnetization reversal in these antidots occurs via field driven transition between 3 elementary magnetization states -termed G, C and Q. These magnetization states can be described by vectors, and the reversal process proceeds via step-wise linear operations on these vector states. Rules governing the co-existence of the three magnetization states were empirically observed. It is shown that in an n × n antidot lattice, a variety of field switchable combinations of G, C and Q can occur, indicating programmability of the antidot lattices.Magnetic antidot lattices are intriguing objects composed of a periodic array of holes (antidots) within an otherwise continuous magnetic film [1][2][3][4][5] . The periodicity of the antidot lattice translates to a periodic magnetization distribution in its ground state, which is disturbed by the application of external magnetic fields. Antidot lattices are therefore ideal testbeds to study the collective behaviour of non-trivial periodic distributions under the influence of external disturbances.The periodicity of antidot lattices makes them viable for applications in magnonic devices, whereby the propagation of spin-waves can be influenced by the lattice geometry 6 . Spin-wave functionality can be dramatically enhanced in devices with programmable magnetization states 7 . Generally in such experiments the collective behaviour of the antidots has been considered -however the local variation of the magnetization around antidots, and their potential for programmability have rarely been taken into account 8 . Controllable switching between magnetization configurations is a desirable feature for devices; for instance in magnonics each configuration may correspond to a specific wave propagation mode thereby realizing a switchable spin-wave filter. Furthermore, antidot lattices possess continuous metallic paths making it possible to perform transport measurements. If the antidot lattice possesses several stable magnetization states, then each state may correspond to a specific magneto-resistance value 9 . To realize the occurrence of antidot lattices with stable magnetization configurations, and to achieve reliable field driven switching between these states; it is essential to understand magnetization reversal mechanisms in antidot lattices.Several previous studies on magnetization reve...

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Magnetization dynamics of nanoscale magnetic materials: A perspective

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Field-controlled ultrafast magnetization dynamics in two-dimensional nanoscale ferromagnetic antidot arrays

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