Neutron Brillouin scattering with pulsed spallation neutron source - spin-wave excitations from ferromagnetic powder samples -

TL;DR

This paper introduces a neutron Brillouin scattering method using a pulsed spallation neutron source, demonstrating its ability to observe ferromagnetic spin waves in powder samples and revealing new insights into their dispersion and energy gaps.

Contribution

The study develops and demonstrates a novel neutron Brillouin scattering technique with a pulsed spallation source, enabling analysis of spin-wave excitations in powder samples.

Findings

Observation of gapless spin waves in La$_{0.8}$Sr$_{0.2}$MnO$_3$

Quadratic Q dependence in SrRuO$_3$ spin-wave dispersion

Large energy gap indicating strong spin-orbit coupling in SrRuO$_3$

Abstract

Neutron Brillouin scattering (NBS) method was developed using a pulsed spallation neutron source, and the feasibility of NBS was demonstrated by observing ferromagnetic spin waves in La$_{0.8}$Sr$_{0.2}$MnO$_3$ and SrRuO$_3$ powders. Gapless spin-wave excitations were observed in La$_{0.8}$Sr$_{0.2}$MnO$_3$, which were continuously extended to the lower scattering vector $Q$ from previous results using single crystals. The novel result is a well-defined quadratic $Q$ dependence in the spin-wave dispersion curve with a large energy gap in SrRuO$_3$ indicating robust spin-orbit coupling.