NORMAL STATE RESISTIVITY OF SINGLE CRYSTALLINE V3Si AS A FUNCTION OF NEUTRON IRRADIATION

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NORMAL STATE RESISTIVITY OF SINGLE

CRYSTALLINE V3Si AS A FUNCTION OF

NEUTRON IRRADIATION

R. Caton, R. Viswanathan

To cite this version:

JOURNAL DE PHYSIQUE Colloque C6, suppl&ment au no 8, Tome 39, aolir 1978, page _C6-385

NORMAL STATE RESISTIVITY O F SINGLE CRYSTALLINE V3Si

AS

A FUNCTION

OF NEUTRON

IRRADIATION+

R. Caton and R. Viswanathan

Brookhaven National ~ a b o r a t d x y , Upton, N e w .York 11973

Rdsumd.- L'analyse de la rdsistivit6 1 l'dtat normal d'un monocristal de V3Si irradiL aux neutrons montre des comportements diffdrents au ddbut et P la fin de la ddgradation de Tc.

Abstract.- Analysis of the normal state resistivity of a neutron damaged single crystal of V3Si shows different behaviours at the beginning and end of degradation of T

.

INTRODUCTION.- In the recent years there has been much interest in the normal state resistivity of A-15 superconductors/l/ and in radiation damage in these superconductors/2/. This investigation was undertaken in hopes of contributing some understan- ding to both areas. Precise normal state resistivi- ty data were taken on a single crystal of V3Si as a function of neutron irradiation. In this way the temperature dependence of the normal state resisti- vity can be followed as the superconducting transi- tion temperature T is systematically depressed.

C'

For the purposes of this paper the data have been analyzed over two temperature regions : A) the full range from 17 K to 300 K, and B) the "high" tempe- rature range with

T L

200 K. Most of the analysis shows one very striking feature in the data. Namely, that the nature of the temperature dependence is essentially unaltered as Tc is degraded from 17 K to 'L 10-7 K and changes considerably as Tc degra- des further.

EXPERIMENT.- The neutron irradiations were carried out in the High Flux Beam Reactor at Brookhaven National Laboratory and the details have been re- ported by Viswanathan and Caton/3/. The resistivity was measured using a standard four probe technique

/3/. The reproducibility of the absolute resistivi- ty was -1: 5 %, the reproducibility of the tempera- ture dependence

*

0.5 % and the precision of the voltage measurement

*

0.1 % or better.

RESULTS AND DISCUSSION.- It has been pointed out that the damage created by the neutron irradiation very possibly is nonuniform/4/. Therefore a work of caution should be interjected at this point,

*

work performed under the auspices of the U.S.

since we have treated the problem in a conventional manner.

A) Full range from 17 K to 300 K.- Figure 1

contains plots of the resistivity p as a function of T for the various irradiations described in ta- ble I. p has been fit to the equation

P

= P O + P ~ T + P ~ ~ -To /T

and the results appear in table I (column 4).

Fig. 1 : The resistivity of the V3Si single crys- tal as a function of temperature for the various neutron irradiations described in table I.

This equation was first introduced by Woodward and Cody/5/ and later used by Williamson et a1.161. Al- though it is not clear what physical meaning this expression has, a correlation has been noted bet- ween To (twice the inflection point) and T

.

the

C '

higher To the lower T 171. However our data is ve- ry striking in that the major changes in To takes place near the end of the degradation in Tc, Testar- di et a1.181 have observed very little change in To down to a T of 12 K in V3Si samples prepared under different conditions.

Department of Energy.

IRXADIATION PLUENCE ( l o l a n/em2) T~ (K) T ~ ( K ) by assuming a limiting value p is "shunting" the

max

o o 16.9 1 1 169

*

5 ideal resistivity p

-

thus

ideal

'

16.9 166

16.0 161 I/P = '/pmaX + '/pideal

We fit to pideal =pideal(o)+LT for the data above

14.0 - . 154

12.3 158 200 K. The analysis (table 11, columns 4,5) does not

7 14.5 10.3 166 show any systematic trend in L. This cduld be due to

8 18.0 9 . 0 180 the restricted temperature range of the fit.

10 25.0 5.7 206 CONCLUSION.- We have shown that there is a very

11 46.1 3.7 3 6 0 * 1 0 striking trend in this data. Analysis using models with parameters which are normally sensitive to T

(i.e. T and B) shows that these parameters are Table I : Fluence, Tc, To for the various neutron

irradiations on the V3Si single crystal. The last essentially unchanged in the initial region of T point(ll)was taken on a polycrystalline sample who-

degradation (down to T = 10-7 K) and change appre- se behaviour at lower fluences was observed to have

the same temperature dependence as for the single ciably as Tc is degraded further. It appears as if crystal. Tc is taken at the midpoint of the transi-

there are two different regions of behaviour and tion.

the degradation of Tc in V3Si perhaps involves two mechanisms. An understanding of this behaviour could B)High temperature region with T

2

200 K.-

lead to a clearer picture of resistivity and defects Gorkhov/9/ has suggested a Rn T dependence for the

in A-15 compounds. resistivity which results from a singularity in the

electron density of states. Since this is a high

temperature limite and Rn T cannot be fit through ACKNOWLEDGEMENTS.- We wish to thank Drs. L. Testar- di and M.P. Sarachik for providing the single crys- an inflection, we have fit only for T

>

200 K to

tal and for helpful discussions and Drs. D. Gurins- get some idea of the behaviour. The results of a fit

ky, M. Suenaga and M. Strongin for their interest. to

appear in table I1 (columns 2 and 3).

References

IWIATION A Wcm) B(K) % (uncm) L ( C I R C ~ ~ K ) / 1 / Superconductivity in d- and f-Band Metals; Ed. by D.H. Douglass (Univ. of Rochester New York,

0 40% 5 5 s 136*5 .6*.2 _{USA) 1976}

3 40 54 138 . 6

/2/ International Conf. on Radiation Effects on Su-

4 36 54 129 .6 perconductivity, Argonne National Lab., USA,

5 34 53 136 . 7 .. 13-16 June 1977, J. Nuc. Mat. (in press)

6 29 54 135 .9 /3/ Viswanathan,R. and Caton, R., Phys.Rev. B(in

press)

7 23 59 145 . 8

8 20 72 158 .6 /4/ Viswanathan,R., Caton,R. and Pande,C.S., J. Low

Temp. Phys.

30

(1978) 503

9 15 71 143 1 . 0

/5/ Woodward,D.W. and Cody,G.D., Phys.Rev.E (1964)

10 12 83 152 . 7 A1 66

5*1 127- 145 . 5 /6/ Williamson,S.J. and Milewits,M., in Superconduc- tivity in d- and £-Band Metals, Ed. by D.H. Douglass (Univ. of Rochester, Rochester, New Table I1 : A, B, p,,, L for the various neutron ir- ~ o r k , USA) 1976 551

radiations on the Y 3 s i single crystal described in

table I. /7/ Fisk,Z., Viswanathan,R., Webb,G.W., Sol. State

Commun.

15

(1974) 1797

/8/ Testardi,L.R., Poate,J.M. and Levinstein,H.J., Testardi et al. have shown a correlation between Phys. Rev.

B15

(1977) 2570

A and B and T in Nb3Ge/8/. Here we see very little /9/ Gorkov,K.P., Sov. Phys. JETP

2

(1974) 830 change in the parameter B to a T- of 10K follo- /lo/ Wiesmann, H., Gurvitch,M., Lutz,H., Gosh,A.,

C:

wed by a substancial change at lower T

c'

Schwarz,B. and Strongin,M., Phys. Rev. Lett. 38 (1977) 782

-