Electronic and nuclear magnetism in PtFex at milli-, and nanokelvin temperatures

Wendler, W.; Herrmannsdörfer, T.; Rehmann, S.; Pobell, F.

doi:10.1209/epl/i1997-00293-9

Cited by 24 publications

(23 citation statements)

References 15 publications

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“…In this paper we show that presence of nodes of the order parameter can lead to a cooling effect. The cooling is reached by adiabatically increasing the supercurrent around a superconducting ring or a cylinder.Currently the lowest temperature of a solid (T ∼ 1µK) is achieved by using a method of adiabatic nuclear demagnetization [2,3]. Spontaneous magnetic ordering of the nuclear magnetic moments represents the low temperature limit for nuclear refrigeration.…”

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confidence: 99%

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Possible cooling effect in high-temperature superconductors

Svidzinsky

2002

Phys. Rev. B

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We show that an adiabatic increase of the supercurrent along a superconductor with lines of nodes of the order parameter on the Fermi surface can result in a cooling effect. The maximum cooling occurs if the supercurrent increases up to its critical value. The effect can also be observed in a mixed state of a bulk sample. An estimate of the energy dissipation shows that substantial cooling can be performed during a reasonable time even in the microkelvin regime.Although the mechanism of high temperature superconductivity still remains unclear there is strong evidence that the order parameter in high temperature superconductors has nodes on the Fermi surface [1]. Such a property is also peculiar to some superconductors with heavy fermions. In this paper we show that presence of nodes of the order parameter can lead to a cooling effect. The cooling is reached by adiabatically increasing the supercurrent around a superconducting ring or a cylinder.Currently the lowest temperature of a solid (T ∼ 1µK) is achieved by using a method of adiabatic nuclear demagnetization [2,3]. Spontaneous magnetic ordering of the nuclear magnetic moments represents the low temperature limit for nuclear refrigeration. The ordering temperature due to nuclear dipole-dipole interaction is typically a fraction of a microkelvin and, therefore, to achieve temperatures lower than 0.1µK a new refrigeration technology is needed. In our cooling mechanism the conduction electrons are cooled during the adiabatic increase of the supercurrent instead of the nuclear spin system being cooled in the nuclear demagnetization process. Further development of the idea of cooling using the phenomena of superconductivity (superfluidity) could be promising to achieve the lowest temperature of solids. Cooling effect in clean superconductorsLet us consider a superconducting ring (or a cylinder) made from a clean high temperature superconductor. For estimates one can assume the Fermi surface to be a cylinder and the order parameter has a simple d-wave form ∆(p) = ∆ 0 cos(2φ), where φ is the polar angle in the ab crystalline plane. Taking into account the real form of the Fermi surface might change numerical coefficients, but these details are not necessary for estimating the magnitude of the cooling effect. Let the c -axis of the superconductor be parallel to the symmetry axis of the ring and the temperature of the system is T ≪ T c , where T c is the superconducting transition temperature.At low temperatures the main contribution to the electronic specific heat of the superconductor arises from quasiparticles that are activated above the gap in narrow vicinities of the nodes of the order parameter. The energy of these quasiparticles is given by

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mentioning

confidence: 99%

“…Currently the lowest temperature of a solid (T ∼ 1µK) is achieved by using a method of adiabatic nuclear demagnetization [2,3]. Spontaneous magnetic ordering of the nuclear magnetic moments represents the low temperature limit for nuclear refrigeration.…”

mentioning

confidence: 99%

Possible cooling effect in high-temperature superconductors

Svidzinsky

2002

Phys. Rev. B

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“…Ein ähnlich ausgeprägter Magnetismus führt beispielsweise in dem Übergangsmetall Rhodium zu der niedrigsten bekannten Sprungtemperatur unter den Elementen (T c (Rh) = 325 mK [4]). Bisherige Untersuchungen an massivem Platin hatten jedoch keine Anzeichen für Supraleitung oder magnetische Ordnung oberhalb der bisher tiefsten erreichten Gleichgewichtstemperatur (der Kernmomente, Elektronen und Gitterschwingungen) von etwa 1,5 mK ergeben [5].…”

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Supraleitung in granularem Platin

1999

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Supraleitung und Ferromagnetismus sind zwei grundlegende, jedoch stark konkurrierende Ordnungsphänomene von Elektronen in Festkörpern. Die meisten Metalle werden bei ausreichend tiefen Temperaturen entweder supraleitend oder sie ordnen magnetisch. Gehen generell alle metallischen Elemente in einen dieser hochgeordneten Zustände über, wenn man sie nur zu hinreichend tiefen Temperaturen abkühlt?

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“…They were the most powerful refrigerators for the microkelvin temperature range, with minimum temperatures of 38 µK achieved in Jülich in 1979 [8], as well as 12 µK in 1987 [9] and 1.5 µK in 1995 [10] in Bayreuth. All these temperatures as well as all the temperatures mentioned in this article are equilibrium temperatures (T electron =T phonon =T nuclei ) measured at metallic samples refrigerated in these apparatus.…”

Section: Experimental Methods At Microkelvin Temperaturesmentioning

confidence: 99%

“…In these experiments a sample of Pt Fe 11ppm was refrigerated to an equilibrium temperature of 1.5 µK (and a nuclear spin temperature of 0.2 µK), (Fig. 10) [10]. Neither for this nor for other bulk Pt samples refrigerated to low 195 Pt nuclei.…”

Section: Platinummentioning

confidence: 98%

Superconductivity at Ultralow Temperatures and Its Interplay with Nuclear Magnetism

Herrmannsdörfer¹,

Pobell²

Frontiers in Superconducting Materials

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Electronic and nuclear magnetism in PtFex at milli-, and nanokelvin temperatures

Cited by 24 publications

References 15 publications

Possible cooling effect in high-temperature superconductors

Possible cooling effect in high-temperature superconductors

Supraleitung in granularem Platin

Superconductivity at Ultralow Temperatures and Its Interplay with Nuclear Magnetism

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