Total interference between nuclear and magnetovibrational one-phonon scattering cross sections

S Raymond,J Persson,N Biniskos,K Schmalzl,T Brückel

doi:10.1088/1742-6596/1316/1/012018

Abstract

A full phonon intensity cancellation is reported in a longitudinal polarized inelastic neutron scattering experiment performed on the magnetocaloric compound MnFe4Si3, a ferromagnet with TCurie ≈ 305 K. The TA[100] phonon polarized along the c-axis measured from the Brillouin zone center G=(0, 0, 2) is observed only in one () of the two non-spin-flip polarization channels and is absent in the other one () at low temperatures. This effect disappears at higher temperatures, in the vicinity of TCurie, where the phonon is measured in both channels with nonetheless marked different intensities. The effect is understood as originating from nuclear-magnetic interference between the nuclear one-phonon and the magnetovibrational one-phonon scattering cross-sections. The total cancellation reported is accidental, i.e. does not correspond to a systematic effect, as established by measurements in different Brillouin zones.

Highlights

Interest for the magnetocaloric effect has been increasing in the last decades in view of applications for room temperature refrigeration [1]
Experimental results The inelastic neutron scattering (INS) experiments were performed on the cold neutron threeaxis spectrometer IN12 [5]
We report a total cancellation of phonon intensity for a given mode in a given Brillouin zone in longitudinal polarized INS measurements

Summary

Introduction

Interest for the magnetocaloric effect has been increasing in the last decades in view of applications for room temperature refrigeration [1]. Neutron scattering studies can bring important microscopic information on the spin and lattice dynamics of these systems and reveal key ingredients at play in their magneto-thermodynamics properties [2, 3, 4]. In such context, experiments were performed on the ferromagnetic compound MnFe4Si3 and the importance of short range magnetic correlations as well as their suppression by a modest magnetic field was highlighted [3]. The aim of the present paper is to describe these effects and to show that they can be explained by the neutron scattering cross-sections

Objectives

Results

Conclusion