All electrical propagating spin wave spectroscopy with broadband wavevector capability

Abstract

We develop an all electrical experiment to perform the broadband phase-resolved spectroscopy of propagating spin waves in micrometer sized thin magnetic stripes. The magnetostatic surface spin waves are excited and detected by scaled down to 125 nm wide inductive antennas, which award ultra broadband wavevector capability. The wavevector selection can be done by applying an excitation frequency above the ferromagnetic resonance. Wavevector demultiplexing is done at the spin wave detector thanks to the rotation of the spin wave phase upon propagation. A simple model accounts for the main features of the apparatus transfer functions. Our approach opens an avenue for the all electrical study of wavevector-dependent spin wave properties including dispersion spectra or non-reciprocal propagation.Spin wave based computing 1 -a paradigm-shifting technology that uses the interference of spin waves-offers potential for significant power and area reduction per computing throughput with respect to complementary metaloxide-semiconductor (CMOS) transistor technology. Efficient solutions for spin wave routing 2,3 , spin wave emission 4 , amplification 1 , and spin wave combination 5,6 have been developed. However, these solutions often rely on materials that are difficult to integrate 7 into a CMOS environment. Moreover, they are often demonstrated only for long wavelength (≥ 1 µm) spin waves, for which the low group velocity limits the speed of computation and communication. Efficient methods to generate and detect spin waves with short wavelengths are still lacking. Inductive methods have commonly been employed for long wavelength spin waves as has Brillouin light scattering spectroscopy 8 , which is however diffraction limited and requires complex procedure to retrieve phase information 9 . Alternative spin wave generation and detection methods based on magneto-elastic coupling in surfaceacoustic wave devices 10 are still under development and raise questions regarding their high frequency capability 11 . Longto-short wavelength conversion can be done in magnonic crystals 12 for a geometrically limited discrete set of wavevectors at the expense of high conversion loss. A better conversion efficiency can be obtained by periodically folded coplanar antennas 13,14 but this at the expense of any flexibility in the generated wavevevector. Overall, none of the above methods has so far demonstrated the combination of phase resolution, broad frequency coverage, high sensitivity, and large wavevector (short wavelength) capability.In this work, we demonstrate that the use of deep submicron inductive antennas can circumvent these limitations and allow for the generation and detection of spin waves with ultra-wide frequency band capability and broad wavevector capability up to 15 − 20 rad/µm. We illustrate our method on micrometer-sized Permalloy stripes and describe its behavior within an analytic framework. Our method complements the advantages of Brillouin Light scattering in a compact all electrical device in which the phase resol...

Unidirectional spin-wave channeling along magnetic domain walls of Bloch type

“…In practice, however, unidirectional spin-wave propagation is not necessarily restricted to this narrow frequency range. Indeed, the normal modes closest in frequency to the gap have profiles such that they hardly couple to laterally homogeneous excitations produced by magnetic field line sources, as those assumed for our numerical simulations, or coplanar waveguide inductive antenna, as most often employed in experiments [27,28]. As a result, the effectively useful frequency window can be much wider, reaching nearly half a GHz in the present case [ Fig.…”

Backward volume vs Damon–Eshbach: A traveling spin wave spectroscopy comparison

“…Single wire antennas have been conventionally used for the study of spin-waves 26 . The inductive fields generated by single wire antenna decay inversely with the distance, and hence, could lead to a strong inductive coupling between the transmitting and receiving antenna.…”

“…The transmission signal of BVSW was found experimentally to be small and comparable to the electromagnetic crosstalk between the two antennas. To better reveal the spin wave signal in the BVSW configuration, the magnetic field derivative of the measured frequency response is used to retain only the SW signal 26 . A low RF power of -10 dBm was used for the measurements.…”

Spin Pinning and Spin-Wave Dispersion in Nanoscopic Ferromagnetic Waveguides

“…It is shown that a critical waveguide width exists, below which the profiles of the spin-wave modes are essentially uniform across the width of the waveguide. This is fundamentally different from the profiles in state-of-the-art waveguides of micrometer [16][17][18][19] or millimeter sizes [25,26], where the profiles are non-uniform and pinned at the waveguide edges due to the dipolar interaction. In nanoscopic waveguides, the exchange interaction suppresses this pinning due to its dominance over the dipolar interaction and, consequently, the exchange interaction defines the profiles of the spin-wave modes as well as the corresponding spin-wave dispersion characteristics.…”