Abstract
We combine micromagnetic simulations and nitrogen-vacancy (NV) defect center spin relaxometry measurements to study magnon modes in inhomogeneous spin textures. A thin, micrometer-scale ferromagnetic disk is magnetized in a vortex state in which the magnetization curls around a central core. Micromagnetic simulations show that at zero applied field, the magnetization dynamics of the disk consist of a low frequency gyrotropic mode and higher frequency azimuthal magnon modes, all far detuned from the NV spin transition frequencies. An in-plane static magnetic field breaks the azimuthal symmetry of the vortex state, resulting in the magnon modes transforming in frequency and spatial profile as the field increases. Experimentally, we probe the dynamics of vortex magnetization as a function of applied in-plane static field and ac driving frequency by optically monitoring a nearby NV defect center spin. At certain values of the applied magnetic field, we observe enhanced spin relaxation when driving at twice the frequency of the NV ground state spin transition in optically detected magnetic resonance measurements. We attribute this effect to parallel pumping of a magnon mode in the disk producing magnons at half the excitation frequency. Micromagnetic simulations support this finding, showing spatial and spectral overlap of a confined magnon mode and an NV spin transition, with sufficient interaction strength to explain the observed signal.
| Original language | English |
|---|---|
| Article number | 073904 |
| Journal | Journal of Applied Physics |
| Volume | 135 |
| Issue number | 7 |
| DOIs | |
| State | Published - Feb 21 2024 |
| Externally published | Yes |
Funding
We acknowledge support from the National Science Foundation (NSF) (Award No. 2326528). Work supported in part (D.D.A. and F.J.H.) by Q-NEXT, a U.S. Department of Energy Office of Science National Quantum Information Science Research Center. Work by S.S.-L. Zhang was also partly supported by the College of Arts and Sciences, Case Western Reserve University. Simulations were performed on the Pennsylvania State University’s Institute for Computational and Data Sciences’ Roar supercomputer with the code developed and tested by using the High Performance Computing Resource in the Core Facility for Advanced Research Computing at Case Western Reserve University. We acknowledge support from the National Science Foundation (NSF) (Award No. 2326528). Work supported in part (D.D.A. and F.J.H.) by Q-NEXT, a U.S. Department of Energy Office of Science National Quantum Information Science Research Center. Work by S.S.-L. Zhang was also partly supported by the College of Arts and Sciences, Case Western Reserve University. Simulations were performed on the Pennsylvania State University’s Institute for Computational and Data Sciences’ Roar supercomputer with the code developed and tested by using the High Performance Computing Resource in the Core Facility for Advanced Research Computing at Case Western Reserve University.