Vortex dynamics and frequency splitting in vertically coupled nanomagnets

M E Stebliy,A V Davydenko,A S Samardak,A V Ognev,A G Kolesnikov,V Khovaylo,J Pearson,L A Chebotkevich,V Novosad,E V Sukovatitcina,J Ding,S Jain

doi:10.1038/s41598-017-01222-4

Abstract

We explored the dynamic response of a vortex core in a circular nanomagnet by manipulating its dipole-dipole interaction with another vortex core confined locally on top of the nanomagnet. A clear frequency splitting is observed corresponding to the gyrofrequencies of the two vortex cores. The peak positions of the two resonance frequencies can be engineered by controlling the magnitude and direction of the external magnetic field. Both experimental and micromagnetic simulations show that the frequency spectra for the combined system is significantly dependent on the chirality of the circular nanomagnet and is asymmetric with respect to the external bias field. We attribute this result to the strong dynamic dipole-dipole interaction between the two vortex cores, which varies with the distance between them. The possibility of having multiple states in a single nanomagnet with vertical coupling could be of interest for magnetoresistive memories.

Highlights

We have demonstrated the successful fabrication of vertically coupled nanomagnets, whose interaction strength dominates the excitation frequencies of two vortex cores present in the nanomagnets
The possibility of having multiple states in a single nanomagnet with vertical coupling could be of interest for magnetoresistive memories
The system of magnetostatically coupled nanodisks was lithographically patterned on coplanar waveguides (CPW) made of Au (300 nm)/Cr (3 nm) with the 4 μm wide and 1.5 mm long signal line

Summary

Introduction

We have demonstrated the successful fabrication of vertically coupled nanomagnets, whose interaction strength dominates the excitation frequencies of two vortex cores present in the nanomagnets. By engineering the direction and magnitude of an external biasing field, specific contrast between the excitation frequencies can be obtained. Due to the asymmetric positioning of the small disk on top of the big disk, asymmetry in the resonance spectra is observed.

Results

Conclusion