[Sur les diagrammes de phase dʼUGe2]
Le mécanisme magnéto-élastique de lʼapparition dʼune instabilité du premier ordre à la transition de phase dans lʼétat ferromagnétique du supraconducteur ferromagnétique itinérant UGe2 est discuté. Une propriété remarquable de ce matériau est la chute abrupte de la température critique au voisinage dʼune pression de 14–15 kbar alors que la température de lʼinstabilité du premier ordre augmente fortement en comparaison de celle-ci. Cet effet qui conduit au changement de la transition du second au premier ordre est également determine par une augmentation de la chaleur spécifique dans un intervalle de températures correspondant au régime des fluctuations critiques. Après avoir effectué les calculs et les estimations nécessaires propres au composé UGe2, nous discutons lʼefficacité de ce mécanisme.
The magneto-elastic mechanism of development of the first order type instability at the phase transition to the ferromagnet state in itinerant ferromagnet-superconductor UGe2 is discussed. The particular property of this material is the precipitous drop of the critical temperature at pressure increase near 14–15 kbar that drastically increases the temperature of the first order instability in respect to the critical temperature. This effect leading to transformation of the second order type transition to the first order one is determined also by the specific heat increase in the temperature interval of the development of critical fluctuations. After performing the necessary calculations and estimations using the parameters characterizing the properties of UGe2 we argue the effectiveness of this mechanism.
Mot clés : Ferromagnétisme, Transitions de phase
@article{CRPHYS_2011__12_5-6_567_0,
author = {Vladimir P. Mineev},
title = {On the phase diagram of {UGe\protect\textsubscript{2}}},
journal = {Comptes Rendus. Physique},
pages = {567--572},
publisher = {Elsevier},
volume = {12},
number = {5-6},
year = {2011},
doi = {10.1016/j.crhy.2011.04.003},
language = {en},
}
Vladimir P. Mineev. On the phase diagram of UGe2. Comptes Rendus. Physique, Volume 12 (2011) no. 5-6, pp. 567-572. doi : 10.1016/j.crhy.2011.04.003. https://comptes-rendus.academie-sciences.fr/physique/articles/10.1016/j.crhy.2011.04.003/
[1] Magnetic quantum phase transition in MnSi under hydrostatic pressure, Phys. Rev. B, Volume 55 (1997), p. 8330
[2] Magnetic quantum phase transition in MnSi, Physica B, Volume 259–261 (1999), p. 847
[3] Phase inhomogeneity of the itinerant ferromagnet MnSi at high pressures, Phys. Rev. Lett., Volume 92 (2004), p. 086403
[4] Phase separation and suppression of critical dynamics at quantum phase transitions of MnSi and (Sr1 − xCax)RuO3, Nat. Phys., Volume 3 (2007), p. 29
[5] Evolution of quasiparticle properties in UGe2 with hydrostatic pressure studied via the de Haas–van Alphen effect, Phys. Rev. Lett., Volume 87 (2001), p. 166401
[6] Magnetic phase diagram and pressure and field dependence of the Fermi surface in UGe2, Phys. Rev. B, Volume 65 (2002), p. 174501
[7] Pressure dependence of the magnetization in the ferromagnetic superconductor UGe2, Phys. Rev. Lett., Volume 89 (2002), p. 147005
[8] A change of the Fermi surface in UGe2 across the critical pressure, J. Phys.: Condens. Matter, Volume 14 (2002), p. L29
[9] Cooperative phenomenon of ferromagnetism and unconventional superconductivity in UGe2: A 73Ge-NQR study under pressure, J. Phys. Soc. Jpn., Volume 74 (2005), p. 2675
[10] Tricritical point and wing structure in the itinerant ferromagnet UGe2, Phys. Rev. Lett., Volume 105 (2010), p. 217201
[11] Quantum phase transitions in the itinerant ferromagnet ZrZn2, Phys. Rev. Lett., Volume 93 (2004), p. 256041
[12] Magnetic properties of the itinerant metamagnetic system Co(S1 − xSex)2 under high magnetic fields and high pressure, Phys. Rev. B, Volume 56 (1997), p. 14019
[13] Evidence for the first-order nature of the ferromagnetic transition in Ni, Fe, Co, and CoFe2O–4, Phys. Rev. B, Volume 78 (2008), p. 174427
[14] Nature of the quantum phase transition in clean itinerant Heisenberg ferromagnets, Phys. Rev. B, Volume 67 (2003), p. 024419
[15] The low-temperature specific heat of metals, Sov. Phys. JETP, Volume 16 (1963), p. 780
[16] Theory of transverse spin dynamics in a polarized Fermi liquid and an itinerant ferromagnet, Phys. Rev. B, Volume 72 (2005), p. 144418
[17] P–T–B magnetic phase diagram of itinerant-electron metamagnets, Physica B, Volume 391 (2007), p. 42
[18] Magnetic disorder as a first-order phase transformation, Phys. Rev., Volume 126 (1961), p. 104
[19] Thermodynamics of phase transitions in compressible solid lattice, J. Chem. Phys., Volume 22 (1954), p. 1535
[20] Statistical Physics, Course of Theoretical Physics, vol. 5, Butterworth–Heinemann, Oxford, 2000
[21] Phase transitions of the first order but nearly of the second, Zh. Eksp. Teor. Fiz., Volume 56 (1969), p. 1664
[22] Phase transition in compressible lattices, Zh. Eksp. Teor. Fiz., Volume 69 (1975), p. 1100 ([ Sov. Phys. JETP, 29, 1969, pp. 1123 ])
[23] Superconductivity on the border of itinerant-electron ferromagnetism in UGe2, Nature, Volume 406 (2000), p. 587
[24] Magnetic and electrical properties of U–Ge intermetallic compounds, J. Phys. Soc. Jpn., Volume 61 (1992), p. 293
[25] Electrodynamics of Continuous Media, Course of Theoretical Physics, vol. VIII, Butterworth–Heinemann, Oxford, 1995
[26] Statistical Physics Part II, Landau and Lifshitz Course of Theoretical Physics, vol. IX, Butterworth–Heinemann, Oxford, 1995
[27] Neutron scattering study of the ferromagnetic superconductor UGe2, Phys. Rev. B, Volume 64 (2001), p. 174509
[28] UGe2: A ferromagnetic spin-triplet superconductor, Phys. Rev. B, Volume 63 (2001), p. 144519
[29] Izv. AN SSSR, Ser. Fiz., 29 (1965), p. 879
[30] Phase transition in uniaxial ferroelectrics, Zh. Eksp. Teor. Fiz., Volume 56 (1969), p. 2087 ([ Sov. Phys. JETP, 42, 1975, pp. 560 ])
[31] Crystal and magnetic structure of the uranium digermanid UGe2, J. Alloys Comp., Volume 247 (1997), p. 104
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