Abstract We studied the magnetic excitations in the quasi-one-dimensional (q-1D) ladder subsystem of Sr 14−x Ca x Cu 24 O 41 (SCCO) using Cu L 3 -edge resonant inelastic X-ray scattering (RIXS). By comparing momentum-resolved RIXS spectra with high ( x = 12.2) and without ( x = 0) Ca content, we track the evolution of the magnetic excitations from collective two-triplon (2 T) excitations ( x = 0) to weakly-dispersive gapped modes at an energy of 280 meV ( x = 12.2). Density matrix renormalization group (DMRG) calculations of the RIXS response in the doped ladders suggest that the flat magnetic dispersion and damped excitation profile observed at x = 12.2 originates from enhanced hole localization. This interpretation is supported by polarization-dependent RIXS measurements, where we disentangle the spin-conserving Δ S = 0 scattering from the predominant Δ S = 1 spin-flip signal in the RIXS spectra. The results show that the low-energy weight in the Δ S = 0 channel is depleted when Sr is replaced by Ca, consistent with a reduced carrier mobility. Our results demonstrate that off-ladder impurities can affect both the low-energy magnetic excitations and superconducting correlations in the CuO 4 plaquettes. Finally, our study characterizes the magnetic and charge fluctuations in the phase frommore »
Parametric resonance of spin waves in ferromagnetic nanowires tuned by spin Hall torque
We present a joint experimental and theoretical study of parametric resonance of spin wave eigenmodes in Ni80Fe20/Pt bilayer nanowires. Using electrically detected magnetic resonance, we measure the spectrum of spin wave eigenmodes in transversely magnetized nanowires and study parametric excitation of these eigenmodes by a microwave magnetic field. We also develop an analytical theory of spin wave eigenmodes and their parametric excitation in the nanowire geometry that takes into account magnetic dilution at the nanowire edges. We measure tuning of the parametric resonance threshold by antidamping spin Hall torque from a direct current for the edge and bulk eigenmodes, which allows us to independently evaluate frequency, damping and ellipticity of the modes. We find good agreement between theory and experiment for parametric resonance of the bulk eigenmodes but signifi cant discrepancies arise for the edge modes. The data reveals that ellipticity of the edge modes is signifi cantly lower than expected, which can be attributed to strong modi fication of magnetism at the nanowire edges. Our work demonstrates that parametric resonance of spin wave eigenmodes is a sensitive probe of magnetic properties at edges of thin-fi lm nanomagnets.
- Award ID(s):
- 1708885
- Publication Date:
- NSF-PAR ID:
- 10357883
- Journal Name:
- Physical review
- ISSN:
- 2469-9985
- Sponsoring Org:
- National Science Foundation
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