Dynamic specific heat near the Curie point of Gd

Jeong, Yoon Hee; Bae, Dalmin; Kwon, Tae-Dong; Moon, Il

doi:10.1063/1.350032

Cited by 12 publications

(6 citation statements)

References 9 publications

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“…This may account for the recent increased interest in ac specific heat measurements. 7,[12][13][14] The main reason for the simplicity of a linear response is the fluctuation-dissipation ͑FD͒ theorem, which expresses the response of a system upon a slight time-dependent change of external parameters in terms of equilibrium fluctuations. In effect, a linear response probes the equilibrium dynamics ͑i.e., the dynamics in absence of any external dis-turbance͒.…”

Section: Introductionmentioning

confidence: 99%

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Fluctuation-dissipation theorem for frequency-dependent specific heat

Nielsen

Dyre

1996

Phys. Rev. B

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A derivation of the fluctuation-dissipation ͑FD͒ theorem for the frequency-dependent specific heat of a system described by a master equation is presented. The FD theorem is illustrated by a number of simple examples, including a system described by a linear Langevin equation, a two-level system, and a system described by the energy master equation. It is shown that for two quite different models with low-energy cutoffs-a collection of two-level systems and a system described by the energy master equation-the frequency-dependent specific heat in dimensionless units becomes universal at low temperatures, i.e., independent of both energy distribution and temperature. These two models give almost the same universal frequencydependent specific heat, which compares favorably to experiments on supercooled alcohols.

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Section: Introductionmentioning

confidence: 99%

“…15 Often, when dealing with the frequency-dependent specific heat, more or less explicit reference is made to the standard FD theorem. 7,12,[16][17][18][19] This, however, is inaccurate since the specific heat is not a response to an external field perturbing the Hamiltonian.…”

Section: Introductionmentioning

confidence: 99%

Fluctuation-dissipation theorem for frequency-dependent specific heat

Nielsen

Dyre

1996

Phys. Rev. B

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“…4 [22,23]. Since the ω component of the ac voltage at the heater causes a spurious signal at the lock-in amplifier, a Wheatstone bridge is used.…”

Section: Methodsmentioning

confidence: 99%

Thermal Conductivity of Chalcogenide As2S3 Thin Films

Kim

Kang

et al. 2004

International Journal of Thermophysics

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In order to investigate the photo-induced thermal property changes in chalcogenide thin films, amorphous As 2 S 3 thin film samples, whose thicknesses are 0.5, 1.0, 2.0, and 4.0 µm, were prepared on silicon wafers by thermal evaporation. Their thermal conductivity was measured by the 3ω method between room temperature and 100 • C. These measurements were repeated after the illumination of an Ar + laser beam whose photon energy is consistent with the bandgap energy of As 2 S 3 , and repeated again for annealed films at 180 • C for 1 h. The result shows that the thermal conductivities of fresh films were 0.14 to 0.27 W · m −1 · K −1 ; however, the values increase to 0.28-0.47 W · m −1 · K −1 after illumination of the sample and decrease to 0.19-0.42 W · m −1 · K −1 after annealing of the sample. These changes can be explained by the change in microstructure produced from the photo-darkening and thermal annealing.

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“…[10][11][12][13][14][15][16][17] Thus low-frequency dynamic specific heat was measured widely. Among the various studies concerning the dynamic specific heat, [10][11][12][13][14][15][16][17][18] we briefly mention two examples in which the origin of the dynamic specific heat was well investigated. The first example was a study using an amorphous dielectric in a low-temperature region.…”

Section: Introductionmentioning

confidence: 99%

Relaxation phenomenon measured as dynamic specific heat in the first-order phase transition of a molecular crystal

et al. 2002

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We found that the specific heat becomes a frequency-dependent complex quantity at and around the two first-order phase transition points of n-hexatriacontane (n-C 36 H 74 ). One is the rotator phase transition point, and the other is the melting point. The dynamic specific heat was measured by using temperature-modulated calorimetry in the low-frequency range of 0.0003р f /Hzр0.05. The frequency range is sufficient to discuss the dispersion of the dynamic specific heat. The dynamic specific heat can be described by the Debye relaxation. The relaxation parameters show different trends in the lower-half temperature region and a higher halftemperature region in each phase transition. We label the former by I R and I M , and the latter as II R and II M (I R and II R are in the rotator phase transition, and I M and II M are in the melting͒. The values of the relaxation time are about 600 s in I R and I M . The values reduce to about 40 s in II R and about 120 s in II M . The relaxation strengths in I R and I M are smaller than those in II R and II M . We found that the thermal conductivity is a real and frequency-independent quantity in the entire temperature region including the phase transition points. The relaxation time of the dynamic specific heat measured in the end of II R agrees with the characteristic time measured by using a polarizing microscope. This agreement reveals that the origin of the obtained dynamic specific heat in the temperature region is the weight fractional fluctuation of the rotator phase.

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Dynamic specific heat near the Curie point of Gd

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Cited by 12 publications

References 9 publications

Fluctuation-dissipation theorem for frequency-dependent specific heat

Fluctuation-dissipation theorem for frequency-dependent specific heat

Thermal Conductivity of Chalcogenide As2S3 Thin Films

Relaxation phenomenon measured as dynamic specific heat in the first-order phase transition of a molecular crystal

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