Effective sound attenuation exponents in magnets

Pawlak, A.; Fechner, Bernhard

doi:10.1002/pssc.200562471

Cited by 9 publications

(5 citation statements)

References 18 publications

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“…Recently, we have studied the temperature, frequency, Onsager coefficient and external magnetic field dependences of sound attenuation near phase transition points for spin-1 and spin-3/2 Ising models on the Bethe lattice for given coordination numbers q in terms of the recursion relations by using the Onsager theory of irreversible thermodynamics [21]. Besides, the behavior of sound attenuation has also been studied for similar systems in which the sound attenuation constant was calculated for one-and two-dimensional ferro-and antiferromagnets [22], the anomalous behavior of the attenuation constant of the longitudinal ultrasonic wave in ferro-and antiferromagnets near the critical point was investigated [23], the critical behavior of sound attenuation and dispersion in a diluted Ising system with a nonconserved order-parameter was studied above the T c [24], the mode-mode coupling theory of Kadanoff and Swift was used to describe the rise in the ultrasonic attenuation as the material approaches its magnetic transition point [25], the sound attenuation and internal friction coefficients were calculated for a realistic model of amorphous silicon [26], a general theory of critical sound propagation was studied in anisotropic magnets above their transition temperature [27], and it was explained how some magnets belonging to the Heisenberg universality class can be characterized by positive sound attenuation exponents near the critical point [28].…”

Section: Introductionmentioning

confidence: 99%

The crystal field effects on sound attenuation for a spin-1 Ising model on the Bethe lattice

Cengiz¹,

Albayrak²

2012

J. Stat. Mech.

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The sound attenuation phenomenon is investigated by using the Onsager theory of irreversible thermodynamics for a spin-1 Ising model with the inclusion of the crystal field effects on the Bethe lattice. The recursion relations are calculated in a transcendental form to obtain the order-parameters and then the sound attenuation is analyzed. The relationships of sound attenuation with temperature, frequency and Onsager coefficient are examined near the secondand first-order phase transition temperatures, T c and T t respectively, for given negative crystal field values and coordination numbers on the Bethe lattice. The sound wave couples to the order-parameter fluctuations which decay mainly via the order-parameter relaxation process. Thus, two relaxation times are obtained which are used to find an expression for the sound attenuation coefficient. The attenuation maxima are found near the second-and first-order phase transition temperatures in the ferromagnetic and quadrupole phase regions, respectively, for the coordination numbers q = 3, 4 and 6. The attenuation peaks are observed at the same temperature before T t and are found to be shifted to lower (higher) temperatures with increasing value of frequency (Onsager coefficient) before T c for any crystal field values. The attenuation peaks are found at lower values and at higher temperatures with negatively increasing crystal field values in the quadrupolar phase regions. In addition, the sound attenuation peaks are also studied at some tricritical points for q = 3, 4 and 6 for some critical values of the crystal field.

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Section: Introductionmentioning

confidence: 99%

The crystal field effects on sound attenuation for a spin-1 Ising model on the Bethe lattice

Cengiz¹,

Albayrak²

2012

J. Stat. Mech.

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Section: Resultsmentioning

confidence: 99%

“…Now, we examine separately the effect of the volume magnetostriction on the thermal conductivity in the vicinity of the phase transition where the phonons can scatter on the fluctuations of the order parameter and on the fluctuations of the spin energy density 21. In general, in magnetic insulators the phonon damping due to critical fluctuations is expected to be proportional to ω 2 /( T − T C ) P , which is directly related to a sound attenuation coefficient 21–23. The quadratic frequency dependence of the coefficient was experimentally observed above a transition temperature in many magnetic insulators with the critical exponent p varying from 0 to the order of 1, depending on the material 21–23.…”

Section: Resultsmentioning

confidence: 99%

The influence of the magnetic subsystem on the heat transport in CsMnCl₃ · 2H₂O

Tkáč¹,

Tibenská²,

Orendáčová³

et al. 2011

Physica Status Solidi (b)

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The thermal conductivity of CsMnCl 3 Á 2H 2 O (CMC) -a quasione-dimensional antiferromagnet with spin 5/2 has been studied in the temperature range from 2 to 25 K in zero magnetic field. The analysis of the data performed within Debye model revealed the combined effect of the single-ion and volume magnetostriction in the vicinity of a phase transition. Thermal-conductivity calculations based on the model and corresponding experimental studies showed that the poor sample quality and small dimensions can suppress the manifestation of a spin-phonon coupling present in CMC.1 Introduction Recent studies of low-dimensional spin systems revealed anomalous thermal transport that can be attributed to magnetic excitations providing an additional heat channel to the system. A large magnetic contribution to the thermal conductivity has been indicated in the S ¼ 1/2 Heisenberg chain Sr 2 CuO 3 , in spin-ladder materials (Ca, La, Sr) 14 Cu 24 O 41 , as well as in the twodimensional Nd 2 CuO 4 and Sr 2 CuO 2 Cl 2 systems [1][2][3][4]. All these materials are characterized by a strong magnetic interaction J/k B % 1000-2000 K, giving rise to a large group magnon velocity related to the magnetic Debye temperature Q m % J/k B , which is much higher than the phonon Debye temperature Q D . The magnon subsystem itself is able to transport heat effectively even at the temperatures where the intensive phonon umklapp scattering significantly reduces the heat transport via a phonon channel. On the other hand, in the systems with a weak magnetic interaction, Q m ( Q D , magnons can be excited over the whole Brillouin zone even at helium temperatures where the phonon channel for the heat transport is strongly suppressed

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“…Furthermore, in magnetic insulators phonon damping due to critical fluctuations of the order parameter occurs, which is proportional to ω 2 /(T − T c ) P1 , which is directly related to the sound attenuation coefficient [45][46][47]. A quadratic frequency dependence of the coefficient has been experimentally observed above a transition temperature in many magnetic insulators, with the critical exponent P1 varying from zero to the order of 1, depending on the material [45][46][47]. A semi-empirical form of the relaxation time has been proposed for the phonon scattering in the + C), where C and D are adjustable parameters which can differ in the ordered and paramagnetic phases [48].…”

Section: Thermal Conductivitymentioning

confidence: 99%

Multiple-timescale relaxation dynamics in CsGd(MoO₄)₂—a dipolar magnet with a highly anisotropic layered crystal structure

Tkáč

Orendáčová

Tarasenko

et al. 2013

J. Phys.: Condens. Matter

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The dynamic properties of the dipolar magnet CsGd(MoO4)2 have been studied. The frequency and temperature dependence of the AC susceptibility investigated in the paramagnetic region above 2 K revealed the co-existence of magnetic field induced slow and fast relaxation channels with a timescale differing by three orders of magnitude. The slow relaxation is determined by the properties of the first coordination sphere of the Gd(3+) ion and has the character of a two-phonon Orbach process. The fast relaxation is potentially attributed to a two-phonon Raman process realized via a localized phonon mode associated with the layered crystal structure. The temperature dependence of the phonon mean free path in zero magnetic field indicates significant phonon scattering below 1 K resulting from the combined effect of magnetic correlations and the scattering of dominant phonons with energies corresponding to the crystal-field levels.

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Effective sound attenuation exponents in magnets

Cited by 9 publications

References 18 publications

The crystal field effects on sound attenuation for a spin-1 Ising model on the Bethe lattice

The crystal field effects on sound attenuation for a spin-1 Ising model on the Bethe lattice

The influence of the magnetic subsystem on the heat transport in CsMnCl₃ · 2H₂O

Multiple-timescale relaxation dynamics in CsGd(MoO₄)₂—a dipolar magnet with a highly anisotropic layered crystal structure

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Effective sound attenuation exponents in magnets

Cited by 9 publications

References 18 publications

The crystal field effects on sound attenuation for a spin-1 Ising model on the Bethe lattice

The crystal field effects on sound attenuation for a spin-1 Ising model on the Bethe lattice

The influence of the magnetic subsystem on the heat transport in CsMnCl3 · 2H2O

Multiple-timescale relaxation dynamics in CsGd(MoO4)2—a dipolar magnet with a highly anisotropic layered crystal structure

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Product

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The influence of the magnetic subsystem on the heat transport in CsMnCl₃ · 2H₂O

Multiple-timescale relaxation dynamics in CsGd(MoO₄)₂—a dipolar magnet with a highly anisotropic layered crystal structure