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Influence of pinning by columnar defects on the longitudinal and hall resistivities of YBa2Cu3O7 single crystals in the mixed state
Journal of Alloys and Compounds, 195 (1993) 415--418 JALCOM 7496
415
Influence of pinning by columnar defects on the longitudinal YBa2Cu307 single crystals in the mixed state
and Hall resistivities
of
A. Legris 1, F. Rullier - Albenque 1, P. Lejay 2 1 CEA / DTA / CEREM / DTM, Laboratoire des Solides Irradi~s, Ecole Polytechnique, 91128 Palaiseau Cedex, F R A N C E 2 CRTBT / CNRS, BP 166X,38042 Grenoble Cedex, FRANCE Absmact We h a v e m e a s u r e d t h e l o n g i t u d i n a l a n d H a l l r e s i s t i v i t i e s of Y B a 2 C u 3 0 7 single c r y s t a l s
irradiated by energetic heavy ions. This type of irradiation results in creation of continuous cylinders of amorphous matter which act as very efficient pinning centers. As a consequence we observe a drastic narrowing of the transition curves in magnetic field ( parallel to the cylinders axis) and a strong increase of the pinning energies near Tc. In addition, the Hall voltage do present a sign change below T c even after irradiation, which confirms that the negative Hall voltage is related to an intrinsic property of the material.
1. I n t r o d u c t i o n Irradiation of h i g h - t e m p e r a t u r e superconduc -tors by different t y p e s of particles h a s been recently u s e d to i n t r o d u c e additional pinning c e n t e r s in t h e s e m a t e r i a l s . Creation of point defects and/or small defect clusters by neutrons, electrons or keV ions irradiation r e s u l t s in a strong e n h a n c e m e n t of magnetic hysteresis and critical c u r r e n t Jc [1-3] . N e v e r t h e l e s s , these defects are efficient only at low t e m p e r a t u r e s and no change in the irreversibility line (IRL) has been observed [3]. On the contrary, columnar defects created by e n e r g e t i c h e a v y ions (such as GeV Pb ) irradiation, act as strong flux pinning centers ( when the magnetic field is parallel to them) in the whole t e m p e r a t u r e range, resulting not only in a d r a m a t i c i n c r e a s e of Jc b u t also in an i m p o r t a n t shift of t h e IRL t o w a r d s h i g h e r t e m p e r a t u r e [4,5]. Creation of such defects is s t r o n g l y r e l a t e d to the v a l u e of the energy deposition by electronic excitation, Se. Indeed, it is now well established [6] t h a t when Se exceeds values of a b o u t 8 keV / nm defects are mainly c r e a t e d via i n e l a s t i c collisions and when it r e a c h e s a t h r e s h o l d of a b o u t 20 k e V / nm, continuous cylindrical a m o r p h o u s latent tracks are produced. In this paper, we present results of transport m e a s u r e m e n t s in the vortex liquid state of low
0925-8388/93/$06.00
fluence (1011 and 2 x 1011 ions / cm 2) Y B a 2 C u 3 0 7 single crystals irradiated with 5.8 GeV Pb ions. In this case, Se is about 33 keV / n m and therefore continuous cylindrical a m o r p h o u s latent tracks with R=3.5 nm are produced in the ratio of one track per incident ion as shown in fig. (1).
Figure 1. Dark field T E M image showing the amorphous tracks in a sample irradiated at 2 x 1011 ions / cm 2. The sample was tilted by 8 ° with respect to the incident beam direction. As r e s u l t of p i n n i n g e n h a n c e m e n t , we o b s e r v e an i m p o r t a n t n a r r o w i n g of t h e resistivity transition curves in magnetic field
© 1993 - Elsevier Sequoia.
All rights reserved
416
A. Legris et al. /Influence of pinning by columnar defects
parallel to the t r a c k axis, while the P x y dependence on magnetic field remains quite the same as in an unirradiated sample.
1.2
.
.
.
.
I
.
.
.
.
I
.
.
.
.
I
"
•
1 0.8
2. E x p e r i m e n t a l 0.6 O .
2.1. Samples Good quality single crystals ( Tc - 92.8 K ) were grown using the standard flux method. Samples were plates of about 2 x 2 x 0,02 mm 3. Good electrical contacts ( contact resistance of about 0.1 £2 ) were performed by sticking Pt wires with silver paste and t h e n performing an annealing at 300 °C for one hour. Resistivity m e a s u r e m e n t s performed on samples I and II i r r a d i a t e d a t 1011 and 2x1011 ions/cm 2 respectively, were made using the standard Van der Pauw method. Hall resistivity m e a s u r e m e n t s were m a d e on sample III irradiated at 10 lz ions / cm 2 by taking the odd voltage contribution when exchanging the voltage and current probes [7]. In all the cases, the current density was limited to 50 A / cm2 and the magnetic field was parallel to the c axis. 2. 2. Irradiation All the samples were irradiated at room temperature at the National Laboratory GANIL* The beam direction was parallel to the c axis and Se ranged from 35 keV/nm, at the entry of the samples and 31 k e V / n m at the end of them. This e n s u r e s t h a t continuous cylinders of amorphous matter with R = 3.5 nm run troughout the whole thickness (see fig. 1).
3. Results a n d D i s c u s s i o n
3.1 Longitudinal resistivity For the low fluences we used, the T¢ reduction was of 0.3 and 0.9 K respectively for the samples irradiated at 1011 and 2 x 1011 ions / cm 2 while the corresponding resistivity increases were of 10 and 20%. Irradiation induces large narrowing of the transition width in presence of magnetic field as displayed in fig. 2, where we have compared the resistivity t r a n s i t i o n s in different magnetic fields for sample II before and after irradiation.
* National Laboratory GANIL - Caen, FRANCE
Q.
0.4 0.2 0 75
80
85
90
95
T(K) 1.2
.
.
.
.
i
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.
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.
i
.
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i
.
.
.
.
0.8 0.6 I °
O.
0.4
// 0.2
;
a.'.
/I11.1. ] 13....
,~.
0 75
80
85
90
95
T(K)
Figure 2. Resistivity transitions in different magnetic fields ( 0,1,2, 4, 6 and 8 T) for sample II before ( upper panel ) and after irradiation (lower panel). We can see for instance that the transition narrowing is about 6 K at 8T, in contrast with r e s u l t s c o n c e r n i n g proton a n d n e u t r o n irradiated YBa2Cu307 single crystals where no significant changes in the transition curves have been observed. Such a narrowing is strongly related to the shift of the irreversibility line towards higher t e m p e r a t u r e s . This clearly appears in fig.3 where we have plotted the irreversibility line as m e a s u r e d by the onset of the longitudinal resistivity for sample II before and after irradiation. This evolution is very similar to t h a t observed by Civale et al [5] after Sn i r a d i a t i o n m e a s u r e d by a c - s u s c e p t i b i l i t y techniques. It is worth mentioning that even if these two m e t h o d s are not an absolute determination of the IRL, they give the same results as those obtained from the vortex glass transition determined from the V ( I ) curves in a single crystal irradiated at 1011 ions/cm2 [7].
A. Legriset aL /Influence of pinning by columnar defects In o r d e r to d e t e r m i n e q u a n t i t a t i v e l y the pinning e n h a n c e m e n t due to the presence of columnar defects, we have carried out detailed analysis of the activated part of the resistivity transitions. F o r this purpose, we have taken a r e s i s t i v i t y d e p e n d e n c e on t e m p e r a t u r e and magnetic field as suggested by Malozemoff et al
[8]: p=poexp(-[Ax(1-t2)3/2/(Hxt)]/kBTc)
(1)
where t = T / Tc. As in [8], we have neglected the P0 dependence on temperature. By fitting the data using formula (1) we obtain different values of A summarized in table 1.
10
8
0
6
•
0
4
O
2
• O QO
0 75
80
85
90
95
T(K) Figure 3. The Pxx = 0 line for sample II before (open circles) a n d after irradiation with 2 x 1011 ions / cm 2 (full circles). We can see t h a t before i r r a d i a t i o n A is around 3 eV x T and is field independent. Such v a l u e s a r e in a g r e e m e n t with p r e v i o u s l y published results (see ref. [8] for instance). After i r r a d i a t i o n we o b s e r v e an i n c r e a s e of the pinning energies as well as a step dependence on magnetic field. For high fields, the e n h a n c e m e n t factor is about 3, while it is close to 6 when we approach fields lower than 2 T. Such a field d e p e n d e n c e evidences the drastic changes in the p i n n i n g m e c h a n i s m s induced by the presence of c o l u m n a r defects. If we define the field B* as the v a l u e of the magnetic field at which the tracks density equalises the flux lines density, then B* = ¢ 0 x ~t where ¢ 0 is the flux q u a n t u m a n d Ct is t h e i r r a d i a t i o n fluence.
417
Within this description, the fluences we used correspond to 2 and 4 T respectively for samples I and II. Such v a l u e s seem to s e p a r a t e two different pinning regimes : for Hext < B* ,there are more t r a c k s t h a n flux lines and then pinning is more efficient t h a n for H e x t > B ' w h e r e the flux lines overtake the number of t r a c k s . W i t h i n each r e g i m e , the p i n n i n g mechanism does not seem to depend on magnetic field, even if irradiations at different fluences should be useful in o r d e r to confirm this observation. 3. 2 Hall resistivity measurements The anomalous behaviour of the Hall effect in the liquid state has a t t r a c t e d an important a t t e n t i o n . Two m a i n p o i n t s h a v e b e e n intensively discussed : the scaling behaviour of the Hall versus longitudinal resistivities (Pxy o¢ Pxx ~ with a close to 2) [9-11] and the sign change just below Tc. Concerning this last point, it has been recently suggested [12] t h a t the negative p a r t of the Hall voltage could be due to the existance of pinning centers in the bulk. If this should be the case, then significant changes in the Hall b e h a v i o u r are expected after introduction of very efficient pinning centers like c o l u m n a r defects. P r e l i m i n a r y r e s u l t s concerning sample III and displayed in fig.4, show that this not seems to be the case.
1 . 2
. . . .
1
"•
=
. . . .
i
. . . .
,
. . . .
i
. . . .
i
. . . .
i
. . . .
i
. . . .
oOd°i
T = 87.5 K
/'.d""' oo
0.8 0.6 0.4
o.e -0. -0.
. . . .
i
1
. . . .
i
2
. . . .
,
3
. . . .
J
.
.
.
4
.
J
5
.
.
.
.
,
6
. . . .
i , , ,
7
H(T) Figure 4. Pxy vs magnetic field at T = 87.5 K for s a m p l e III before (open circles) and after irradiation at 1011 ions/cm 2 (full squares).
418
A. Legris et al. /Influence of pinning by columnar defects
Table 1.Summary of the A values for samples I and II at different magnetic fields before and after irradiation
Hext ( T ) 0,5 1 2 4 6 8
A (eV.T) sample I before irradiation
A (eV.T) sample I after irradiation
3.6 3.3
20.1 24.9 24.2 16 10.2 9.3
Indeed we can see that within our experimental accuracy there is no significant modifications in the Pxy dependence on magnetic field - for a fixed temperature close to Tc - excepted a shift t o w a r d s h i g h e r fields. N e v e r t h e l e s s , more accurate m e a s u r e m e n t s are needed to study the Pxy vs Pxx curves in the activated regime in order to examine if the scaling form Pxy o¢ Pxx a holds after irradiation .
4. C o n c l u s i o n
In this paper, we have studied by means of t r a n s p o r t m e a s u r e m e n t s , t h e i n f l u e n c e of irratliation induced columnar defects on the t r a n s p o r t p r o p e r t i e s in the liquid state of YB2Cu307 single crystals. Our results confirm t h a t a new pinning mechanism, different from the one induced by point defects or randomly d i s t r i b u t e d clusters of defects, have to be considered in order to explain not only the shift of the irreversibily line but also the existence of two different pinning regimes in the activated region, separated by B*. Moreover, it seems clear that the negative part of the Hall voltage below T c is not a pinning consequence. Acknowledgments It is a pleasure to t h a n k Prof. Goshchiskii who gave us sample III and Dr. S. Bouffard for participating in the irradiation experiments. References
[1] J. Gianpintzakis, M. A~ Kirk, W. C. Lee, J. P. Rice, D. M. Ginsberg, I. M. Robertson, R.
A (eV.T) sample II before irradiation 2.9 2.6 2.9 2.4 2.5
A (eV.T) sample II after irradiation 18.1 20.1 19.3 12.9 10.8 10.9
L. Wheeler.- Proceedings of Symposium S of the MRS Spring 1992 Meeting. [2] F. M. Sauerzopf, H.P. Wiesinger, W. Kritscha, and H. W. Weber. Phys. Rev. B 43, 3091 (1991). [3] L. Civale, A~ D. Marwick, M. W. McElfresh, T. K. Worthington, A. P. Malozemoff, F. Holtzberg, J. R. Thompson, and M. A. Kirk, Phys. Rev. Lett. 65, 1164 (1990). [4] M. Konczykowski, F. Rullier-Albenque, E. R. Yacoby, A. Shaulov, Y. Yeshurun and P. Lejay. Phys. Rev. B 44, 7167 (1991). [5] L. Civale, A. D. Marwick, T. K. Worthington, M. A. Kirk, J. R. Thompson, L. Krushin-Elbaum, Y. Sun, J. R. Clem, and F. Holtzberg. Phys.Rev.Lett. 67, 648 (1991). [6] A. Legris, F. Rullier - Albenque, A. Barbu, H. Pascard, S. Bouffard, E. Paumier, and P. Lejay. Proceedings of SHIM 92. To be published in Radiation Effects and Defects in Solids. [7] A. Legris and F. Rullier-Albenque, to be published. [8] A. P. Malozemoff, T. K. Worthington, E.Zeldov, N. C. Yeh, M.W. McElfresh and F. Holtzberg. Strong Correlation and Superconductivity, ed. H. Fukuyama, S. Maekawa and A. P. Malozemoff. Springer, Heidelberg 1989. [9] V. M. Vinokur, V. B. Geskenbein, M. V. Feigel'man, and G. Blatter. To be published. [10] A. T. Dorsey and M. P. A. Fisher. Phys. Rev. Lett. 68, 694 (1992) [11] J. Luo, T.P. Orlando, J. M. Graybeal. X. D. Wu, and R. Muenchausen. Phys. Rev. Lett. 68, 690 (1992). [12] Z.D. Wang and C.S. Ting. Phys. Rev. B 46, 284 (1992).
415
Influence of pinning by columnar defects on the longitudinal YBa2Cu307 single crystals in the mixed state
and Hall resistivities
of
A. Legris 1, F. Rullier - Albenque 1, P. Lejay 2 1 CEA / DTA / CEREM / DTM, Laboratoire des Solides Irradi~s, Ecole Polytechnique, 91128 Palaiseau Cedex, F R A N C E 2 CRTBT / CNRS, BP 166X,38042 Grenoble Cedex, FRANCE Absmact We h a v e m e a s u r e d t h e l o n g i t u d i n a l a n d H a l l r e s i s t i v i t i e s of Y B a 2 C u 3 0 7 single c r y s t a l s
irradiated by energetic heavy ions. This type of irradiation results in creation of continuous cylinders of amorphous matter which act as very efficient pinning centers. As a consequence we observe a drastic narrowing of the transition curves in magnetic field ( parallel to the cylinders axis) and a strong increase of the pinning energies near Tc. In addition, the Hall voltage do present a sign change below T c even after irradiation, which confirms that the negative Hall voltage is related to an intrinsic property of the material.
1. I n t r o d u c t i o n Irradiation of h i g h - t e m p e r a t u r e superconduc -tors by different t y p e s of particles h a s been recently u s e d to i n t r o d u c e additional pinning c e n t e r s in t h e s e m a t e r i a l s . Creation of point defects and/or small defect clusters by neutrons, electrons or keV ions irradiation r e s u l t s in a strong e n h a n c e m e n t of magnetic hysteresis and critical c u r r e n t Jc [1-3] . N e v e r t h e l e s s , these defects are efficient only at low t e m p e r a t u r e s and no change in the irreversibility line (IRL) has been observed [3]. On the contrary, columnar defects created by e n e r g e t i c h e a v y ions (such as GeV Pb ) irradiation, act as strong flux pinning centers ( when the magnetic field is parallel to them) in the whole t e m p e r a t u r e range, resulting not only in a d r a m a t i c i n c r e a s e of Jc b u t also in an i m p o r t a n t shift of t h e IRL t o w a r d s h i g h e r t e m p e r a t u r e [4,5]. Creation of such defects is s t r o n g l y r e l a t e d to the v a l u e of the energy deposition by electronic excitation, Se. Indeed, it is now well established [6] t h a t when Se exceeds values of a b o u t 8 keV / nm defects are mainly c r e a t e d via i n e l a s t i c collisions and when it r e a c h e s a t h r e s h o l d of a b o u t 20 k e V / nm, continuous cylindrical a m o r p h o u s latent tracks are produced. In this paper, we present results of transport m e a s u r e m e n t s in the vortex liquid state of low
0925-8388/93/$06.00
fluence (1011 and 2 x 1011 ions / cm 2) Y B a 2 C u 3 0 7 single crystals irradiated with 5.8 GeV Pb ions. In this case, Se is about 33 keV / n m and therefore continuous cylindrical a m o r p h o u s latent tracks with R=3.5 nm are produced in the ratio of one track per incident ion as shown in fig. (1).
Figure 1. Dark field T E M image showing the amorphous tracks in a sample irradiated at 2 x 1011 ions / cm 2. The sample was tilted by 8 ° with respect to the incident beam direction. As r e s u l t of p i n n i n g e n h a n c e m e n t , we o b s e r v e an i m p o r t a n t n a r r o w i n g of t h e resistivity transition curves in magnetic field
© 1993 - Elsevier Sequoia.
All rights reserved
416
A. Legris et al. /Influence of pinning by columnar defects
parallel to the t r a c k axis, while the P x y dependence on magnetic field remains quite the same as in an unirradiated sample.
1.2
.
.
.
.
I
.
.
.
.
I
.
.
.
.
I
"
•
1 0.8
2. E x p e r i m e n t a l 0.6 O .
2.1. Samples Good quality single crystals ( Tc - 92.8 K ) were grown using the standard flux method. Samples were plates of about 2 x 2 x 0,02 mm 3. Good electrical contacts ( contact resistance of about 0.1 £2 ) were performed by sticking Pt wires with silver paste and t h e n performing an annealing at 300 °C for one hour. Resistivity m e a s u r e m e n t s performed on samples I and II i r r a d i a t e d a t 1011 and 2x1011 ions/cm 2 respectively, were made using the standard Van der Pauw method. Hall resistivity m e a s u r e m e n t s were m a d e on sample III irradiated at 10 lz ions / cm 2 by taking the odd voltage contribution when exchanging the voltage and current probes [7]. In all the cases, the current density was limited to 50 A / cm2 and the magnetic field was parallel to the c axis. 2. 2. Irradiation All the samples were irradiated at room temperature at the National Laboratory GANIL* The beam direction was parallel to the c axis and Se ranged from 35 keV/nm, at the entry of the samples and 31 k e V / n m at the end of them. This e n s u r e s t h a t continuous cylinders of amorphous matter with R = 3.5 nm run troughout the whole thickness (see fig. 1).
3. Results a n d D i s c u s s i o n
3.1 Longitudinal resistivity For the low fluences we used, the T¢ reduction was of 0.3 and 0.9 K respectively for the samples irradiated at 1011 and 2 x 1011 ions / cm 2 while the corresponding resistivity increases were of 10 and 20%. Irradiation induces large narrowing of the transition width in presence of magnetic field as displayed in fig. 2, where we have compared the resistivity t r a n s i t i o n s in different magnetic fields for sample II before and after irradiation.
* National Laboratory GANIL - Caen, FRANCE
Q.
0.4 0.2 0 75
80
85
90
95
T(K) 1.2
.
.
.
.
i
.
.
.
.
i
.
.
.
.
i
.
.
.
.
0.8 0.6 I °
O.
0.4
// 0.2
;
a.'.
/I11.1. ] 13....
,~.
0 75
80
85
90
95
T(K)
Figure 2. Resistivity transitions in different magnetic fields ( 0,1,2, 4, 6 and 8 T) for sample II before ( upper panel ) and after irradiation (lower panel). We can see for instance that the transition narrowing is about 6 K at 8T, in contrast with r e s u l t s c o n c e r n i n g proton a n d n e u t r o n irradiated YBa2Cu307 single crystals where no significant changes in the transition curves have been observed. Such a narrowing is strongly related to the shift of the irreversibility line towards higher t e m p e r a t u r e s . This clearly appears in fig.3 where we have plotted the irreversibility line as m e a s u r e d by the onset of the longitudinal resistivity for sample II before and after irradiation. This evolution is very similar to t h a t observed by Civale et al [5] after Sn i r a d i a t i o n m e a s u r e d by a c - s u s c e p t i b i l i t y techniques. It is worth mentioning that even if these two m e t h o d s are not an absolute determination of the IRL, they give the same results as those obtained from the vortex glass transition determined from the V ( I ) curves in a single crystal irradiated at 1011 ions/cm2 [7].
A. Legriset aL /Influence of pinning by columnar defects In o r d e r to d e t e r m i n e q u a n t i t a t i v e l y the pinning e n h a n c e m e n t due to the presence of columnar defects, we have carried out detailed analysis of the activated part of the resistivity transitions. F o r this purpose, we have taken a r e s i s t i v i t y d e p e n d e n c e on t e m p e r a t u r e and magnetic field as suggested by Malozemoff et al
[8]: p=poexp(-[Ax(1-t2)3/2/(Hxt)]/kBTc)
(1)
where t = T / Tc. As in [8], we have neglected the P0 dependence on temperature. By fitting the data using formula (1) we obtain different values of A summarized in table 1.
10
8
0
6
•
0
4
O
2
• O QO
0 75
80
85
90
95
T(K) Figure 3. The Pxx = 0 line for sample II before (open circles) a n d after irradiation with 2 x 1011 ions / cm 2 (full circles). We can see t h a t before i r r a d i a t i o n A is around 3 eV x T and is field independent. Such v a l u e s a r e in a g r e e m e n t with p r e v i o u s l y published results (see ref. [8] for instance). After i r r a d i a t i o n we o b s e r v e an i n c r e a s e of the pinning energies as well as a step dependence on magnetic field. For high fields, the e n h a n c e m e n t factor is about 3, while it is close to 6 when we approach fields lower than 2 T. Such a field d e p e n d e n c e evidences the drastic changes in the p i n n i n g m e c h a n i s m s induced by the presence of c o l u m n a r defects. If we define the field B* as the v a l u e of the magnetic field at which the tracks density equalises the flux lines density, then B* = ¢ 0 x ~t where ¢ 0 is the flux q u a n t u m a n d Ct is t h e i r r a d i a t i o n fluence.
417
Within this description, the fluences we used correspond to 2 and 4 T respectively for samples I and II. Such v a l u e s seem to s e p a r a t e two different pinning regimes : for Hext < B* ,there are more t r a c k s t h a n flux lines and then pinning is more efficient t h a n for H e x t > B ' w h e r e the flux lines overtake the number of t r a c k s . W i t h i n each r e g i m e , the p i n n i n g mechanism does not seem to depend on magnetic field, even if irradiations at different fluences should be useful in o r d e r to confirm this observation. 3. 2 Hall resistivity measurements The anomalous behaviour of the Hall effect in the liquid state has a t t r a c t e d an important a t t e n t i o n . Two m a i n p o i n t s h a v e b e e n intensively discussed : the scaling behaviour of the Hall versus longitudinal resistivities (Pxy o¢ Pxx ~ with a close to 2) [9-11] and the sign change just below Tc. Concerning this last point, it has been recently suggested [12] t h a t the negative p a r t of the Hall voltage could be due to the existance of pinning centers in the bulk. If this should be the case, then significant changes in the Hall b e h a v i o u r are expected after introduction of very efficient pinning centers like c o l u m n a r defects. P r e l i m i n a r y r e s u l t s concerning sample III and displayed in fig.4, show that this not seems to be the case.
1 . 2
. . . .
1
"•
=
. . . .
i
. . . .
,
. . . .
i
. . . .
i
. . . .
i
. . . .
i
. . . .
oOd°i
T = 87.5 K
/'.d""' oo
0.8 0.6 0.4
o.e -0. -0.
. . . .
i
1
. . . .
i
2
. . . .
,
3
. . . .
J
.
.
.
4
.
J
5
.
.
.
.
,
6
. . . .
i , , ,
7
H(T) Figure 4. Pxy vs magnetic field at T = 87.5 K for s a m p l e III before (open circles) and after irradiation at 1011 ions/cm 2 (full squares).
418
A. Legris et al. /Influence of pinning by columnar defects
Table 1.Summary of the A values for samples I and II at different magnetic fields before and after irradiation
Hext ( T ) 0,5 1 2 4 6 8
A (eV.T) sample I before irradiation
A (eV.T) sample I after irradiation
3.6 3.3
20.1 24.9 24.2 16 10.2 9.3
Indeed we can see that within our experimental accuracy there is no significant modifications in the Pxy dependence on magnetic field - for a fixed temperature close to Tc - excepted a shift t o w a r d s h i g h e r fields. N e v e r t h e l e s s , more accurate m e a s u r e m e n t s are needed to study the Pxy vs Pxx curves in the activated regime in order to examine if the scaling form Pxy o¢ Pxx a holds after irradiation .
4. C o n c l u s i o n
In this paper, we have studied by means of t r a n s p o r t m e a s u r e m e n t s , t h e i n f l u e n c e of irratliation induced columnar defects on the t r a n s p o r t p r o p e r t i e s in the liquid state of YB2Cu307 single crystals. Our results confirm t h a t a new pinning mechanism, different from the one induced by point defects or randomly d i s t r i b u t e d clusters of defects, have to be considered in order to explain not only the shift of the irreversibily line but also the existence of two different pinning regimes in the activated region, separated by B*. Moreover, it seems clear that the negative part of the Hall voltage below T c is not a pinning consequence. Acknowledgments It is a pleasure to t h a n k Prof. Goshchiskii who gave us sample III and Dr. S. Bouffard for participating in the irradiation experiments. References
[1] J. Gianpintzakis, M. A~ Kirk, W. C. Lee, J. P. Rice, D. M. Ginsberg, I. M. Robertson, R.
A (eV.T) sample II before irradiation 2.9 2.6 2.9 2.4 2.5
A (eV.T) sample II after irradiation 18.1 20.1 19.3 12.9 10.8 10.9
L. Wheeler.- Proceedings of Symposium S of the MRS Spring 1992 Meeting. [2] F. M. Sauerzopf, H.P. Wiesinger, W. Kritscha, and H. W. Weber. Phys. Rev. B 43, 3091 (1991). [3] L. Civale, A~ D. Marwick, M. W. McElfresh, T. K. Worthington, A. P. Malozemoff, F. Holtzberg, J. R. Thompson, and M. A. Kirk, Phys. Rev. Lett. 65, 1164 (1990). [4] M. Konczykowski, F. Rullier-Albenque, E. R. Yacoby, A. Shaulov, Y. Yeshurun and P. Lejay. Phys. Rev. B 44, 7167 (1991). [5] L. Civale, A. D. Marwick, T. K. Worthington, M. A. Kirk, J. R. Thompson, L. Krushin-Elbaum, Y. Sun, J. R. Clem, and F. Holtzberg. Phys.Rev.Lett. 67, 648 (1991). [6] A. Legris, F. Rullier - Albenque, A. Barbu, H. Pascard, S. Bouffard, E. Paumier, and P. Lejay. Proceedings of SHIM 92. To be published in Radiation Effects and Defects in Solids. [7] A. Legris and F. Rullier-Albenque, to be published. [8] A. P. Malozemoff, T. K. Worthington, E.Zeldov, N. C. Yeh, M.W. McElfresh and F. Holtzberg. Strong Correlation and Superconductivity, ed. H. Fukuyama, S. Maekawa and A. P. Malozemoff. Springer, Heidelberg 1989. [9] V. M. Vinokur, V. B. Geskenbein, M. V. Feigel'man, and G. Blatter. To be published. [10] A. T. Dorsey and M. P. A. Fisher. Phys. Rev. Lett. 68, 694 (1992) [11] J. Luo, T.P. Orlando, J. M. Graybeal. X. D. Wu, and R. Muenchausen. Phys. Rev. Lett. 68, 690 (1992). [12] Z.D. Wang and C.S. Ting. Phys. Rev. B 46, 284 (1992).