Competition of lattice and spin excitations in the temperature dependence of spin-wave properties

DI GENNARO, Marco, MIRANDA, Alonso L, OSTLER, Thomas, ROMERO, Aldo H and VERSTRAETE, Matthieu J (2018). Competition of lattice and spin excitations in the temperature dependence of spin-wave properties. Physical Review B (PRB), 97 (21).

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The interplay of magnons and phonons can induce strong temperature variations in the magnetic exchange interactions, leading to changes in the magnetothermal response. This is a central mechanism in many magnetic phenomena, and in the new field of Spin Caloritronics, which focuses on the combination of heat and spin currents. Boson model systems have previously been developed to describe the magnon phonon coupling, but until recently studies rely on empirical parameters. In this work we propose a first principles approach to describe the dependence of the magnetic exchange integrals on phonon renormalization, leading to changes in the magnon dispersion as a function of temperature. The temperature enters into the spin dynamics (by introducing fluctuations) as well as in the magnetic exchange itself. Depending on the strength of the coupling, these two temperatures may or may not be equilibrated, yielding different regimes. We test our approach in typical and well known ferromagnetic materials: Ni, Fe, and Permalloy. We compare our results to recent experiments on the spin-wave stiffness, and discuss departures from Bloch’s law and parabolic dispersion.

Item Type: Article
Additional Information: Article number : 214417
Research Institute, Centre or Group: Materials and Engineering Research Institute > Polymers Nanocomposites and Modelling Research Centre
Departments: Faculty of Science, Technology and Arts > Engineering and Mathematics
Identification Number:
Depositing User: Thomas Ostler
Date Deposited: 12 Jun 2018 10:21
Last Modified: 23 Jun 2018 19:14

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