Room-temperature magnetic thermal switching by suppressing phonon-magnon scattering

Fanghao Zhang, Lokanath Patra, Yubi Chen, Wenkai Ouyang, Paul M. Sarte, Shantal Adajian, Xiangying Zuo, Runqing Yang, Tengfei Luo, and Bolin Liao

Phys. Rev. B 109, 184411 – Published 6 May 2024

Abstract

Thermal switching materials, whose thermal conductivity can be controlled externally, show great potential in contemporary thermal management. The manipulation of thermal transport properties through magnetic fields has been accomplished in materials that exhibit a high magnetoresistance. However, it is generally understood that the lattice thermal conductivity attributed to phonons is not significantly impacted by the magnetic fields. In this study, we experimentally demonstrate the significant impact of phonon-magnon scattering on the thermal conductivity of the rare-earth metal gadolinium near room temperature, which can be controlled by a magnetic field to realize thermal switching. Using first-principles lattice dynamics and spin-lattice dynamics simulations, we attribute the observed change in phononic thermal conductivity to field-suppressed phonon-magnon scattering. This research suggests that phonon-magnon scattering in ferromagnetic materials is crucial to determine their thermal conductivity, opening the door to innovative magnetic-field-controlled thermal switching materials.

Received 10 January 2024
Revised 4 April 2024
Accepted 22 April 2024

DOI:https://doi.org/10.1103/PhysRevB.109.184411

Physics Subject Headings (PhySH)

Lattice dynamics Magnetotransport Magnons Phonons Thermal conductivity

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Fanghao Zhang ¹, Lokanath Patra¹, Yubi Chen ^2,1, Wenkai Ouyang¹, Paul M. Sarte³, Shantal Adajian ¹, Xiangying Zuo¹, Runqing Yang¹, Tengfei Luo⁴, and Bolin Liao ^1,*

¹Department of Mechanical Engineering, University of California, Santa Barbara, California 93106-5070, USA
²Department of Physics, University of California, Santa Barbara, California 93106-9530, USA
³Material Research Laboratory, University of California, Santa Barbara, California 93106, USA
⁴Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, Indiana 46556, USA

^*bliao@ucsb.edu

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Vol. 109, Iss. 18 — 1 May 2024

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Images

Figure 1
(a) The schematic of the experimental setup. (b) Measured thermal conductivity of single-crystalline Gd as a function of temperature without an external field. The inset shows the data near the Curie temperature. The thermal conductivity shows a minima around its Curie temperature (293 K). (c) Measured thermal conductivity of single-crystalline Gd as a function of the external magnetic field at different temperatures. The external magnetic field increases the thermal conductivity near the Curie temperature. (d) The switching ratio of the thermal conductivity of Gd under a 9 T magnetic field. Error bars represent random uncertainties from three repeated measurements. More discussion of the random and systematic errors in our measurements is provided in Appendix pp1.
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Figure 2
(a) Measured electrical resistivity of the single-crystal Gd as a function of temperature without a magnetic field. The resistivity shows a general metal trend consistent with previously reported data. (b) The measured electrical resistance of single-crystalline Gd as a function of an external magnetic field at different temperatures. A negative magnetoresistance is measured at all temperatures. A small up-turn of the resistance at 293 K and 7 T is within the uncertainty of the measurement. (c) The electronic thermal conductivity of Gd as a function of an external magnetic field at different temperatures. The electronic thermal conductivity is calculated by applying the Wiedemann-Franz law to the electrical resistivity data. (d) The phononic contribution to the thermal conductivity of single-crystalline Gd as a function of an external magnetic field at different temperatures. The phononic contribution is estimated by subtracting the electronic contribution from the total thermal conductivity using the Wiedemann-Franz law.
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Figure 3
(a) Comparison of the experimentally measured phononic thermal conductivity of single-crystalline Gd without an external magnetic field ( $κ_{P h}$ _EXP) to the results from first-principles lattice dynamics ( $κ_{P h}$ _LD) and spin-lattice dynamics ( $κ_{P h}$ _SLD) simulations. (b) Comparison of the experimentally measured magnetic field dependence of the phononic thermal conductivity in single-crystalline Gd to the spin-lattice dynamics simulation results at different temperatures. The $T_{c}$ simulated from SLD is 300 K, while the $T_{c}$ obtained from experiments is 293 K. (c) The phonon spectral energy density (SED) evaluated at $q = [0.25, 0, 0]$ from the SLD simulation as a function of an external magnetic field. The two lowest peaks, corresponding to the TA and LA acoustic modes, are fitted to a Lorentzian function to extract their linewidths. (d) The extracted peak linewidth of the TA and LA modes in single-crystalline Gd from the SLD simulation as a function of an external magnetic field up to 9 T. The observed narrowing of the SED peak linewidth in the presence of an external magnetic field suggests suppression of phonon scattering by the field.
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Figure 4
Calculated Lorenz number in Gd at different temperatures using DFT within the constant relaxation time approximation. The black dashed horizontal line indicates the reference value of the Lorenz number, $2.44 \times 10^{- 8} V^{2} K^{- 2}$ .
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