Thermal characterisation of a tungsten magnetoresistive heat switch

Bartlett, J.; Hardy, Gareth; Hepburn, I. D.; Ray, Rajat; Weatherstone, S.

doi:10.1016/j.cryogenics.2010.02.027

Cited by 23 publications

(12 citation statements)

References 8 publications

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“…By operating the dADRs in a tandem configuration (i.e. one dADR is recycled whilst the second provides cooling), the thermal interface can be maintained at a constant temperature thereby providing continuous cooling at any user-specified temperature in the range of 100 mK to 4 K. In the mKCC, single crystal tungsten magnetoresistive heat switches are used [2]. Detailed information on the mKCC is given in Bartlett et al [1]).…”

Section: Introductionmentioning

confidence: 98%

Design and performance of a fast thermal response miniature Chromium Potassium Alum (CPA) salt pill for use in a millikelvin cryocooler

Bartlett¹,

Hardy²,

Hepburn³

2015

Cryogenics

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a b s t r a c tThe design and performance of a fast thermal response miniature (24 mm outer diameter by 30 mm long) Chromium Potassium Alum (CPA) salt pill is described. The need for a fast thermal response has been driven by the development of a continuously operating millikelvin cryocooler (mKCC) which uses 2 T superconducting magnets that can be ramped to full field in 30 s. The consequence of magnetising and demagnetising the CPA pill in such a short time is that thermal boundary resistance and eddy current heating have a significant impact on the performance of the pill, which was investigated in detail using modelling. The complete design of a prototype CPA pill is described in this paper, including the methods used to minimise thermal boundary resistance and eddy current heating as well as the manufacturing and assembly processes. The performance of the prototype CPA pill operated from a 3.6 K bath is presented, demonstrating that a complete CPA cycle (magnetising, cooling to bath and demagnetising) can be accomplished in under 2.5 min, with magnetisation and demagnetisation taking just 30 s each. The cold finger base temperature of the prototype varies with demagnetisation speed as a consequence of eddy current heating; for a 30 s demagnetisation, a base temperature of 161 mK is obtained, whilst for a 5 min demagnetisation, a base temperature of 149 mK was measured (both from a 3.6 K and 2 T starting position). The measured hold times of the CPA pill at 200 mK, 300 mK, and 1 K are given, proving that the hold time far exceeds the recycle time and demonstrating the potential for continuous operation when two ADRs are used in a tandem configuration. The ease and speed at which the CPA pill temperature can be changed and controlled when stepping between operating temperatures in the range of 200 mK to 4 K using a servo control program is also shown, once again highlighting the excellent thermal response of the pill. All of the test results are in good agreement with the modelling used to design the CPA pill, giving good confidence in our ability to understand and estimate the effects of eddy current heating and thermal boundary resistance. To conclude, the design for the CPA pill to be used in the mKCC (which is heavily based on the design of the prototype) is presented.

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Section: Introductionmentioning

confidence: 98%

Design and performance of a fast thermal response miniature Chromium Potassium Alum (CPA) salt pill for use in a millikelvin cryocooler

Bartlett¹,

Hardy²,

Hepburn³

2015

Cryogenics

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“…This fact has attracted interest in the use of high-purity tungsten as a low temperature heat switch which might be applied in adiabatic demagnetisation refrigerators (ADRs) [12][13][14][15]. These refrigerators generally operate below 4 K and are one of the main technologies for accessing temperatures below the liquid helium regime.…”

Section: Introductionmentioning

confidence: 99%

Thermal Magnetoconductivity of Tungsten Below 6 K: Combining the Zero-, Low- and High-Field Cases

et al. 2014

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We present a phenomenological expression to describe the thermal magnetoconductivity of tungsten which unifies the zero-field thermal conductivity with the low and high-field cases. Its basic form is derived from semi-classical magnetoresistance theory with fitting parameters allowing adjustment to particular samples. Thermal conductivity measurements at 5.5 K and in fields from 0 to 2 T are presented on two single crystals of tungsten with significantly different purities. We find thatwith suitable adjustment of the fitting parameters-the equation is an excellent fit to the data in both cases. The significance of the fitting parameters and differences in their values are discussed, and we describe how they can be related to the individual properties of the samples. It is concluded that the equation should be applicable to any field below that at which orbit quantisation occurs and temperatures from 6 K down to tungsten's superconducting transition.

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“…Co 3 V 2 O 8 has a crystal lattice with space group Cmca. 2,3 The edge sharing CoO 6 octahedra form a staircase kagomé structure and the kagomé staircase lattices are separated by the nonmagnetic VO 4 tetrahedra (see Fig. S1 of the Supplementary Material 15 ).…”

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“…The presence of two different Co 2+ sites along with competing interactions such as the single-ion anisotropy, the nearest-neighbor and the next nearest-neighbor exchanges, and Dzyaloshinskii-Moriya (DM) interactions lead to fascinating magnetic behaviors at low temperatures. [1][2][3][16][17][18][19][20]22,23 In zero field, there are successive magnetic transitions from the paramagnetic (PM) to incommensurate antiferromagnetic (ICAF), commensurate antiferromagnetic (CAF) and commensurate ferromagnetic phases (CF). 1,19 The geometric frustration results in an antiferromagnetic order of Co 2+ spins at a rather low temperature of T N = 11.4 K. 2,16,18 At T N , only the Co 2+ spins locating in the spine site order antiferromagnetically along the a axis.…”

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“…They have wide and important applications in not only the cryogenics but also the deep space detectors, space coolers and spacecrafts. [1][2][3][4] A famous heat switch used in cryogenic cryostat is made by metal superconductors, whose electronic thermal conductivity can be switched on by applying magnetic field to suppress the superconductivity. 1 This kind of heat switch works only at very low temperatures (well below the superconducting transition temperatures or at subKelvin temperatures).…”

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Heat switch effect in an antiferromagnetic insulator Co3V2O8

Zhao

et al. 2016

Applied Physics Letters

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We report a heat switch effect in single crystals of an antiferromagnet Co 3 V 2 O 8 , that is, the thermal conductivity (κ) can be changed with magnetic field in an extremely large scale. Due to successive magnetic phase transitions at 12-6 K, the zero-field κ(T ) displays a deep minimum at 6.7 K and rather small magnitude at low temperatures. Both the temperature and field dependencies of κ demonstrate that the phonons are strongly scattered at the regime of magnetic phase transitions. Magnetic field can suppress magnetic scattering effect and significantly recover the phonon thermal conductivity. In particular, a 14 T field along the a axis increases the κ at 7.5 K up to 100 times. For H c, the magnitude of κ can be suppressed down to ∼ 8% at some field-induced transition and can be enhanced up to 20 times at 14 T. The present results demonstrate that it is possible to design a kind of heat switch in the family of magnetic materials. Heat switches are devices that switch as needed between roles of good thermal conductors and good thermal insulators. They have wide and important applications in not only the cryogenics but also the deep space detectors, space coolers and spacecrafts. 1-4 A famous heat switch used in cryogenic cryostat is made by metal superconductors, whose electronic thermal conductivity can be switched on by applying magnetic field to suppress the superconductivity. 1 This kind of heat switch works only at very low temperatures (well below the superconducting transition temperatures or at subKelvin temperatures). Since the phonon thermal conductivity at such low temperatures are negligibly small, the total thermal conductivity can be changed by several orders of magnitude with magnetic field, a nearly ideal thermal insulator to good thermal conductor transition. At not very low temperatures, the thermal conductivity (κ) of any materials usually cannot be significantly changed by control parameter, 5,6 since there is always sizeable phonon thermal conductivity which is not easily changed much. However, past decades studies on the heat transport of magnetic materials have revealed that the phonon thermal conductivity can be remarkably changed by magnetic field in the case there is strong scattering between phonons and magnetic excitations. 7-12 In partica) Electronic mail: lxgrz@ustc.edu.cn b) Electronic mail: xfsun@ustc.edu.cn ular, a large magnetic-field-induced increase of κ can be observed in rare-earth manganites and titanates. 10,11 In this Letter, we report exceptionally large magnetothermal conductivity in an antiferromagnetic insulator, Co 3 V 2 O 8 . As large as 100 times increase of κ in magnetic field was found at temperature of several kelvins. The result provides a possible route to find heat switch devices that can work at not very low temperatures.Co 3 V 2 O 8 has a crystal lattice with space group Cmca. 2,3 The edge sharing CoO 6 octahedra form a staircase kagomé structure and the kagomé staircase lattices are separated by the nonmagnetic VO 4 tetrahedra (see Fig. S1 of the Sup...

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Thermal characterisation of a tungsten magnetoresistive heat switch

Cited by 23 publications

References 8 publications

Design and performance of a fast thermal response miniature Chromium Potassium Alum (CPA) salt pill for use in a millikelvin cryocooler

Design and performance of a fast thermal response miniature Chromium Potassium Alum (CPA) salt pill for use in a millikelvin cryocooler

Thermal Magnetoconductivity of Tungsten Below 6 K: Combining the Zero-, Low- and High-Field Cases

Heat switch effect in an antiferromagnetic insulator Co3V2O8

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