Brillouin-Mandelstam Spectroscopy of Stress-Modulated Spatially Confined Spin Waves in Ni Thin Films on Piezoelectric Heterostructures

TL;DR

This study uses Brillouin-Mandelstam spectroscopy to investigate stress-controlled spin waves in Ni thin films on piezoelectric substrates, revealing how voltage-induced strain modulates confined magnon modes for potential spintronic applications.

Contribution

It demonstrates the first observation of stress-modulated, spatially confined spin wave modes in Ni films on piezoelectric heterostructures, combining experimental and theoretical analysis.

Findings

Identification of the first two PSSW modes in Ni films.

Voltage-induced strain causes a downshift in PSSW frequencies.

Non-monotonic frequency dependence linked to pinning changes.

Abstract

We report results of micro-Brillouin-Mandelstam light scattering spectroscopy of thermal magnons in the two-phase synthetic multiferroic structure consisting of a piezoelectric (PMN-PT) substrate and a Ni thin film with the thickness of 64 nm. The experimental data reveal the first two modes of the perpendicular standing spin waves (PSSW) spatially confined across the Ni thin film. A theoretical analysis of the frequency dependence of the PSSW peaks on the external magnetic field reveals the asymmetric boundary condition, i.e. pinning, for variable magnetization at different surfaces of the Ni thin film. The strain field induced by applying DC voltage to PMN-PT substrate leads to a down shift of PSSW mode frequency owing to the magneto-elastic effect in Ni, and corresponding changes in the spin wave resonance conditions. The observed non-monotonic dependence of the PSSW frequency on DC voltage is related to an abrupt change of the pinning parameter at certain values of the voltage. The obtained results are important for understanding the thermal magnon spectrum in ferromagnetic films and development of the low-power spin-wave devices.