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Alexander N. Taldenkov

Bio: Alexander N. Taldenkov is an academic researcher from Kurchatov Institute. The author has contributed to research in topics: Thermal conductivity & Magnetization. The author has an hindex of 18, co-authored 110 publications receiving 1358 citations.


Papers
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Journal ArticleDOI
TL;DR: In this article, the authors measured the thermal conductivity of seven germanium crystals with different isotopic compositions in the temperature range between 2 K and 300 K. The experimental data have been fitted with the full Callaway theory, modified by treating transverse and longitudinal modes separately, using three free adjustable parameters for each set of modes to represent anharmonic effects plus the calculated contributions from isotopic and boundary scattering.
Abstract: We have measured the thermal conductivity of seven germanium crystals with different isotopic compositions in the temperature range between 2 K and 300 K. These samples, including one made of highly enriched ${}^{70}\mathrm{Ge}(99.99%)$, show intrinsic behavior at room temperature with the exception of a $p$-type sample with $|{N}_{d}\ensuremath{-}{N}_{a}|\ensuremath{\cong}2\ifmmode\times\else\texttimes\fi{}{10}^{16} {\mathrm{cm}}^{\ensuremath{-}3}$. The ``undoped'' samples exhibit a ${T}^{3}$ dependence at low temperatures, basically determined by boundary scattering. The maximum value of $\ensuremath{\kappa}$ (which falls in the range between 13 K and 23 K) is found to be a monotonically decreasing function of the isotopic mass variance parameter $g$. The maximum ${\ensuremath{\kappa}}_{m}$ measured for the most highly enriched ${}^{70}\mathrm{Ge}(99.99%)$ sample is 10.5 kW/mK, one order of magnitude higher than for natural germanium. The experimental data have been fitted with the full Callaway theory, modified by treating transverse and longitudinal modes separately, using three free adjustable parameters for each set of modes to represent anharmonic effects plus the calculated contributions from isotopic and boundary scattering. For the isotopically purest ${}^{70}\mathrm{Ge}(99.99%)$ sample, dislocation scattering, or a similar mechanism, must be added in order to fit the data. We have also checked the effect of various surface treatments on the thermal conductivity in the low temperature region. The highest values of $\ensuremath{\kappa}$ are found after polish etching with a SYTON suspension.

356 citations

Journal ArticleDOI
TL;DR: The thermal conductivity of isotopically enriched 28Si (enrichment better than 99.9%) was redetermined independently in three laboratories by high precision experiments on a total of four samples of different shape and degree of isotope enrichment in the range from 5 to 300 K with particular emphasis on the range near room temperature as mentioned in this paper.

117 citations

Journal ArticleDOI
TL;DR: The thermal conductivity of single crystals of silicon with two different isotopic compositions: natural and 99.983% enriched 28Si, was investigated in the temperature range from 0.5 K to 300 K as discussed by the authors.
Abstract: The thermal conductivity κ(T) of single crystals of silicon with two different isotopic compositions: natural and 99.983% enriched 28Si, was investigated in the temperature range from 0.5 K to 300 K. The enriched 28Si sample has very high thermal conductivity maximum of 290 W cm–1K–1 at Tmax = 26.5 K, about 7.5 times higher relative to the conductivity of natSi with natural isotope abundance. The isotope effect decreases with temperature increase, being 10 ± 2% at room temperature. The data are discussed briefly within the Ambegaocar's theory of isotope effect. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

104 citations

Journal ArticleDOI
TL;DR: In this article, the phonon Hall effect in the paramagnetic dielectric garnet Tb3Ga5O12 has been investigated and it has been found that the coefficient of the PHE is positive and is equal to (3.5 ± 2) × 10−5T−1 in a magnetic field of 3 T at a temperature of 5.13 K.
Abstract: The phonon Hall effect in the paramagnetic dielectric garnet Tb3Ga5O12 has been investigated. It has been found that the coefficient of the phonon Hall effect is positive and is equal to (3.5 ± 2) × 10−5T−1 in a magnetic field of 3 T at a temperature of 5.13 K. The results are experimental evidence of the phonon Hall effect in the paramagnetic dielectric found by C. Strohm, G. L. J. A. Rikken, and P. Wyder, Phys. Rev. Lett. 95, 155901 (2005).

76 citations

Journal ArticleDOI
TL;DR: In this article, a set of expressions for the anharmonic phonon scattering processes (normal and umklapp) has been proposed which gives an excellent fit to the experimental data over almost the whole temperature range explored.
Abstract: Thermal conductivity of three high purity synthetic single crystalline diamonds has been measured with high accuracy at temperatures from 6 to 410 K. The crystals grown by chemical vapor deposition and by high-pressure high-temperature technique demonstrate almost identical temperature dependencies $\ensuremath{\kappa}(T)$ and high values of thermal conductivity, up to 24 $\mathrm{W}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$ at room temperature. At conductivity maximum near 63 K, the magnitude of thermal conductivity reaches 285 $\mathrm{W}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$, the highest value ever measured for diamonds with the natural carbon isotope composition. Experimental data were fitted with the classical Callaway model for the lattice thermal conductivity. A set of expressions for the anharmonic phonon scattering processes (normal and umklapp) has been proposed which gives an excellent fit to the experimental $\ensuremath{\kappa}(T)$ data over almost the whole temperature range explored. The model provides the strong isotope effect, nearly 45%, and the high thermal conductivity ($g24$ $\mathrm{W}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$) for the defect-free diamond with the natural isotopic abundance at room temperature.

76 citations


Cited by
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TL;DR: The thermal properties of carbon materials are reviewed, focusing on recent results for graphene, carbon nanotubes and nanostructured carbon materials with different degrees of disorder, with special attention given to the unusual size dependence of heat conduction in two-dimensional crystals.
Abstract: Recent years have seen a rapid growth of interest by the scientific and engineering communities in the thermal properties of materials. Heat removal has become a crucial issue for continuing progress in the electronic industry, and thermal conduction in low-dimensional structures has revealed truly intriguing features. Carbon allotropes and their derivatives occupy a unique place in terms of their ability to conduct heat. The room-temperature thermal conductivity of carbon materials span an extraordinary large range--of over five orders of magnitude--from the lowest in amorphous carbons to the highest in graphene and carbon nanotubes. Here, I review the thermal properties of carbon materials focusing on recent results for graphene, carbon nanotubes and nanostructured carbon materials with different degrees of disorder. Special attention is given to the unusual size dependence of heat conduction in two-dimensional crystals and, specifically, in graphene. I also describe the prospects of applications of graphene and carbon materials for thermal management of electronics.

5,189 citations

Journal ArticleDOI
TL;DR: In this paper, a large variety of experiments reviewed in detail here contain results compatible with the theoretical predictions, including phase diagrams of manganite models, the stabilization of the charge/orbital/spin ordered half-doped correlated electronics (CE)-states, the importance of the naively small Heisenberg coupling among localized spins, the setup of accurate mean-field approximations, and the existence of a new temperature scale T∗ where clusters start forming above the Curie temperature, the presence of stripes in the system, and many others.

2,927 citations

Journal ArticleDOI
TL;DR: ShengBTE is a software package for computing the lattice thermal conductivity of crystalline bulk materials and nanowires with diffusive boundary conditions based on a full iterative solution to the Boltzmann transport equation.

1,834 citations

Journal ArticleDOI
TL;DR: In this article, a toolkit of familiar electronic analogs for use of phononics is put forward, i.e., phononic devices are described which act as thermal diodes, thermal transistors, thermal logic gates, and thermal memories.
Abstract: The form of energy termed heat that typically derives from lattice vibrations, i.e., phonons, is usually considered as waste energy and, moreover, deleterious to information processing. However, in this Colloquium, an attempt is made to rebut this common view: By use of tailored models it is demonstrated that phonons can be manipulated similarly to electrons and photons, thus enabling controlled heat transport. Moreover, it is explained that phonons can be put to beneficial use to carry and process information. In the first part ways are presented to control heat transport and to process information for physical systems which are driven by a temperature bias. In particular, a toolkit of familiar electronic analogs for use of phononics is put forward, i.e., phononic devices are described which act as thermal diodes, thermal transistors, thermal logic gates, and thermal memories. These concepts are then put to work to transport, control, and rectify heat in physically realistic nanosystems by devising practical designs of hybrid nanostructures that permit the operation of functional phononic devices; the first experimental realizations are also reported. Next, richer possibilities to manipulate heat flow by use of time-varying thermal bath temperatures or various other external fields are discussed. These give rise to many intriguing phononic nonequilibrium phenomena such as, for example, the directed shuttling of heat, geometrical phase-induced heat pumping, or the phonon Hall effect, which may all find their way into operation with electronic analogs.

1,157 citations

Journal Article
TL;DR: In this paper, it was shown that the itinerant ferromagnetic order persists in Fe3GeTe2 down to the monolayer with an out-of-plane magnetocrystalline anisotropy.
Abstract: Materials research has driven the development of modern nano-electronic devices. In particular, research in magnetic thin films has revolutionized the development of spintronic devices1,2 because identifying new magnetic materials is key to better device performance and design. Van der Waals crystals retain their chemical stability and structural integrity down to the monolayer and, being atomically thin, are readily tuned by various kinds of gate modulation3,4. Recent experiments have demonstrated that it is possible to obtain two-dimensional ferromagnetic order in insulating Cr2Ge2Te6 (ref. 5) and CrI3 (ref. 6) at low temperatures. Here we develop a device fabrication technique and isolate monolayers from the layered metallic magnet Fe3GeTe2 to study magnetotransport. We find that the itinerant ferromagnetism persists in Fe3GeTe2 down to the monolayer with an out-of-plane magnetocrystalline anisotropy. The ferromagnetic transition temperature, Tc, is suppressed relative to the bulk Tc of 205 kelvin in pristine Fe3GeTe2 thin flakes. An ionic gate, however, raises Tc to room temperature, much higher than the bulk Tc. The gate-tunable room-temperature ferromagnetism in two-dimensional Fe3GeTe2 opens up opportunities for potential voltage-controlled magnetoelectronics7-11 based on atomically thin van der Waals crystals.

1,017 citations