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Non-Equilibrium Heat Transport in Pt and Ru Probed by an Ultrathin Co Thermometer
Materials Science · Submitted 28 Dec 2019
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim In this work, we demonstrate that the magnetization of a sub-nm-thick Co layer with perpendicular magnetic anisotropy can effectively serve as a thermometer to monitor non-equilibrium dynamics in adjacent metals, Pt and Ru, via time-resolved magneto-optic Kerr effect.
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The abstract, sentence by sentence
Non-equilibrium of electrons, phonons, and magnons in metals is a fundamental phenomenon in condensed matter physics and serves as an important driver in the field of ultrafast magnetism. In this work, we demonstrate that the magnetization of a sub-nm-thick Co layer with perpendicular magnetic anisotropy can effectively serve as a thermometer to monitor non-equilibrium dynamics in adjacent metals, Pt and Ru, via time-resolved magneto-optic Kerr effect. The temperature evolutions of the Co thermometer embedded in Pt layers of different thicknesses, 6-46 nm, are adequately described by a phenomenological three temperature model with a consistent set of materials parameters. We do not observe any systematic deviations between the model and the data that can be caused by a non-thermal distribution of electronic excitations. We attribute the consistently good agreement between the model and the data to strong electron-electron interaction in Pt. By using Pt/Co/Pt and Pt/Co/Pt/Ru structures, we determine the electron-phonon coupling parameters of Pt and Ru, g_ep(Pt)=(6+/-1)x10^17 W m-3 K-1 and g_ep(Ru)=(9+/-2)x10^17 W m-3 K-1. We also find that the length scales of non-equilibrium between electrons and phonons are l_ep=({\Lambda}_e/g_ep)^1/2 =9 nm for Pt and 7 nm for Ru, shorter than their optical absorption depths, 11 and 13 nm, respectively. Therefore, the optically thick Pt and Ru layers show two steps of temperature rise: The initial jump of electron temperature that occurs within 1 ps is caused by direct optical excitation and electronic heat transport within a distance l_ep for the Co layer. The second temperature rise is caused by heat transport by electrons and phonons that are near thermal equilibrium. We contrast two-temperature modeling of heat transport in Pt an Ru films to calculations for Cu, which has a much longer non-equilibrium length scale, l_ep=63 nm.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | Non-equilibrium of electrons, phonons, and magnons in metals is a fundamental phenomenon in condensed matter physics and serves as an important driver in the field of ultrafast magnetism. | background 1.00 | 0.03 | 0.03 | asserted 1.00 |
| s1 | In this work, we demonstrate that the magnetization of a sub-nm-thick Co layer with perpendicular magnetic anisotropy can effectively serve as a thermometer to monitor non-equilibrium dynamics in adjacent metals, Pt and Ru, via time-resolved magneto-optic Kerr effect. | contribution 0.98 | 0.96 | 0.51 | asserted 1.00 |
| s2 | The temperature evolutions of the Co thermometer embedded in Pt layers of different thicknesses, 6-46 nm, are adequately described by a phenomenological three temperature model with a consistent set of materials parameters. | result 0.95 | 0.95 | 0.14 | asserted 0.98 |
| s3 | We do not observe any systematic deviations between the model and the data that can be caused by a non-thermal distribution of electronic excitations. | result 0.99 | 0.96 | 0.13 | asserted 0.97 |
| s4 | We attribute the consistently good agreement between the model and the data to strong electron-electron interaction in Pt. | interpretation 1.00 | 0.79 | 0.16 | asserted 0.93 |
| s5 | By using Pt/Co/Pt and Pt/Co/Pt/Ru structures, we determine the electron-phonon coupling parameters of Pt and Ru, g_ep(Pt)=(6+/-1)x10^17 W m-3 K-1 and g_ep(Ru)=(9+/-2)x10^17 W m-3 K-1. | result 1.00 | 0.98 | 0.25 | asserted 1.00 |
| s6 | We also find that the length scales of non-equilibrium between electrons and phonons are l_ep=({\Lambda}_e/g_ep)^1/2 =9 nm for Pt and 7 nm for Ru, shorter than their optical absorption depths, 11 and 13 nm, respectively. | result 1.00 | 0.96 | 0.12 | asserted 1.00 |
| s7 | Therefore, the optically thick Pt and Ru layers show two steps of temperature rise: The initial jump of electron temperature that occurs within 1 ps is caused by direct optical excitation and electronic heat transport within a distance l_ep for the Co layer. | interpretation 0.85 | 0.88 | 0.19 | asserted 1.00 |
| s8 | The second temperature rise is caused by heat transport by electrons and phonons that are near thermal equilibrium. | interpretation 0.80 | 0.83 | 0.09 | asserted 1.00 |
| s9 | We contrast two-temperature modeling of heat transport in Pt an Ru films to calculations for Cu, which has a much longer non-equilibrium length scale, l_ep=63 nm. | interpretation 0.33 | 0.83 | 0.08 | asserted 0.97 |
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Original abstract
Non-equilibrium of electrons, phonons, and magnons in metals is a fundamental phenomenon in condensed matter physics and serves as an important driver in the field of ultrafast magnetism. In this work, we demonstrate that the magnetization of a sub-nm-thick Co layer with perpendicular magnetic anisotropy can effectively serve as a thermometer to monitor non-equilibrium dynamics in adjacent metals, Pt and Ru, via time-resolved magneto-optic Kerr effect. The temperature evolutions of the Co thermometer embedded in Pt layers of different thicknesses, 6-46 nm, are adequately described by a phenomenological three temperature model with a consistent set of materials parameters. We do not observe any systematic deviations between the model and the data that can be caused by a non-thermal distribution of electronic excitations. We attribute the consistently good agreement between the model and the data to strong electron-electron interaction in Pt. By using Pt/Co/Pt and Pt/Co/Pt/Ru structures, we determine the electron-phonon coupling parameters of Pt and Ru, g_ep(Pt)=(6+/-1)x10^17 W m-3 K-1 and g_ep(Ru)=(9+/-2)x10^17 W m-3 K-1. We also find that the length scales of non-equilibrium between electrons and phonons are l_ep=({\Lambda}_e/g_ep)^1/2 =9 nm for Pt and 7 nm for Ru, shorter than their optical absorption depths, 11 and 13 nm, respectively. Therefore, the optically thick Pt and Ru layers show two steps of temperature rise: The initial jump of electron temperature that occurs within 1 ps is caused by direct optical excitation and electronic heat transport within a distance l_ep for the Co layer. The second temperature rise is caused by heat transport by electrons and phonons that are near thermal equilibrium. We contrast two-temperature modeling of heat transport in Pt an Ru films to calculations for Cu, which has a much longer non-equilibrium length scale, l_ep=63 nm.
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