THERMAL BOUNDARY RESISTANCE BETWEEN LIQUID 3He AND COPPER POTASSIUM TUTTON SALT

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Submitted on 1 Jan 1978

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THERMAL BOUNDARY RESISTANCE BETWEEN

LIQUID 3He AND COPPER POTASSIUM TUTTON

SALT

Y. Fujii, M. Kubota, H. Matsumoto, Y. Tanaka, T. Shigi

To cite this version:

JOURNAL DE PHYSIQUE Colloque C6, supplement au n" 8, Tome 39, aout 1978, page C6-267

THERMAL BOUNDARY RESISTANCE BETWEEN LIQUID

He AND COPPER POTASSIUM TUTTON SALT

Y. Fujii, M. Kubota, H. Matsumoto, Y. Tanaka and T. Shigi

Faculty of Science, Osaka City University, Suginoto-Cho, Svmiyoehi-ku, Osaka, Japan

Résumé.- Nous avons mesuré la résistance thermique de contact entre 1' He liquide et le sel de tutton de Cuivre et de Potassium (CPS) dans la gamme de température entre 8,5 et 110 mK. Le CPS présente une

température de transition (T ) d'apparence ferromagnétique à 29,5 mK. La résistance de contact est proportionnelle à T au-dessus de T et à T-^5 entre T et 15 mK mis à part une singularité à 29,3 mK. Abstract.- The thermal boundary resistance between liquid 3He and copper potassium tutton salt (CPS) was measured in the temperature range of 8.5 mK to 110 mK. The CPS turned out to have the ferroma-gnetic-like transition temperature (T ) at 29.5 mK. The boundary resistance was proportional to T above T and to T-1-5 between T and lS mK, except for a sharp dip at 29.3 mK.

c c

In 1966 Abel et al. IM found that the ther-mal boundary resistance between liquid 3He and CMN became smaller below 20 mK than expected from the normal Kapitza resistance. This phenomenon was ex-plained as the magnetic coupling between the He nu-clear spins and the CMN electron spins. In order to see the behavior of magnetic coupling above and be-low the magnetic transition temperature of a magne-tic salt, we measured the boundary resistance bet-ween liquid 3He and copper potassium tutton salt, CuK., ( 3 0 ^ . 6 ^ 0 , (CPS).

The measuring cell made of Stycast 1266 is shown in figure 1. This is thermally connected to

average particle diameter 'V 60 ym) was packed in the Epibond 100 A case which was inserted into the cell by using soap seal. The total amount of liquid 3He

(''He concentration less than several ppm) in the cell was 4.6 cm3. Powdered CMN (9.3 mg) was used to measure the cell temperature. The 16-Hz susceptibi-lities of CPS and CMN were measured with an ac mu-tual inductance bridge employing a SQUID as a null detector. At first, the temperature dependence of

16-Hz susceptibility of CPS was measured, which is shown in figure 2. The magnetic transition

tempera-Fig. 1 : Schematic diagram of experimental cell. A : 3He inlet tube. B : Copper brush (thermally connected to mixer). C : Heater. D : CMN. E : Se-condary coil (astatic pair). F : Primary coil. G : Lead shield. H : Magnetic field coil. I : CPS. J : Secondary coil (astatic pair). K : Primary coil. L : Soap seal. M : Coil foil hardened with Epibond

100 A (thermally connected to mixer).

the mixer of a dilution refrigerator by a fine cop-per wire brush. The specimen of powdered CPS 10.4 mg,

St/ca*t IZic

mm EpLbond 100A

Fig. 2 Temperature dependence of the apparent 16_Hz susceptibility (bridge reading) of CPS

ture (T = 29.54 ± 0.15 mK) agrees with the tempe-rature of the specific heat jump (29.5 ± 0.2 mK) measured by M. Rayl 111. Below T the temperature variation of the susceptibility becomes small, but one can see a little minimum and maximum as shown in the insertion.

To change the temperature of CPS from the

ambient liquid 3 ~ e

temperature the dc magnetic field pond to the strong magnetic coupling effect found by

was applied or removed by a superconducting coil

S. Saito

at higher temperatures. However, it is

wound outside the cell. The time constant for the

noteworthy that the present anomaly is seen at a ve-

thermal equilibrium between CPS and liquid 3 ~ e

was

ry low temperature where liquid 3 ~ e

degenerates al-

determined by recording the recovery of the CPS tem- most completely.

perature (actually the susceptibility of CPS) to

the ambient 3 ~ e

temperature. The observed recovery

curve seemed to consist of two exponential decays.

References

We think that this effect is due to the thermal re-

sistance of liquid 3He along the narrow channels

Abel, W.R., Anderson, A.C., Black, W.C. and

amoung the salt powders. In the case of the powdered

Wheatley, J.C., Phys. Rev. Lett.

16,

sample

this

Rayl, K., Thesis, University of Illinois

specific heat of CMN is about two orders smaller

Leggett,

and Vuorio, M.,

Low Temp. Phys.

3 359 (1970)

-

than that of CPS. We adopted the first decay for de-

/4/

Mills, D.L. and Beal-Monod, M.T., Phys. Rev.

termining the time constant between liquid 3 ~ e

and

CPS.

Mills, D.L. and Beal-Monod, M.T., Phys. Rev.

The heat capacity of liquid 3 ~ e

was always

significantly greater than that of CPS in the pre-

Saito, S., Phys. Rev. Lett.

2,

Saito, S., Sato, T., Hanawa, M., Osanai,

H. and

sent case, so that the time constant

can be con-

Nishina,

Y., Proc. ULT Hakond Symposium,

nected to the boundary resistance R as

RCcps.

As for the heat capacity of CPS, Ccps, we used the

data measured by M. Rayl in the temperature rangeof

20

to

The observed temperature dependence

the thermal resistance is shown in figure

It is

Fig.

The boundary resistance between liquid 3 ~ e

and CPS. The smooth extrapolation of spe-

cific heat data by Rayl were used below

mK

proportional to T above T as expected from the

theories

and to ~-5' between T and

as

expected from the theory of Mills et al.

But

below

the temperature dependence of the

thermai resistance seems to change to the minus

higher power of temperature, if Rayl's data is smo-

othly extrapolated.

At

just below Tc the thermal resis-