Resistivity anisotropy and Josephson coupling in
lead-substituted bismuth cuprates
F.-X. Régi, J. Schneck, H. Savary, R. Mellet, P. Müller, R. Kleiner
To cite this version:
F.-X. Régi, J. Schneck, H. Savary, R. Mellet, P. Müller, et al.. Resistivity anisotropy and
Josephson coupling in lead-substituted bismuth cuprates. Journal de Physique III, EDP Sciences, 1994, 4 (11), pp.2249-2257. <10.1051/jp3:1994270>. <jpa-00249259>
HAL Id: jpa-00249259
https://hal.archives-ouvertes.fr/jpa-00249259
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Phys.
J.
iii
Franc-e
(1994)
4
2249-2257
1994,
NOVEMBER
2249
PAGE
Classification
Physic-s
Abstracts
74.70J
74.50
Resistivity
anisotropy
substituted
Rdgi ('),
F.-X.
Kleiner
(')
France
(2)
J.
Institut,
partielle
de
adjacents,
1994,
du
des
rdsultats
bismuth
le
par
ces
plans.
Dans
la
direction
dans
cette
:
:
2
:
results
decrease
phase,
it
forces
sans
resistivity
the
increases
along
intermediate
Il
intercalation.
Dans
the
Bi-O
In
up
to
5 000
A/cm~
liaison
de
2,
:1:
plans
entre
Bi-O
l'intercalation
effet
diminuer
de
elle
le
augmente
plus
courant
des
la
peut
critique
caractdristiques
de
que
2
sur
le plomb a pour
supraconductrice,
ainsi
:
I-V
intermddiaires.
showing
possibility
planes,
the
Bi-2
rdsultats
densitds
des
5000A/cm~,
branches
results
par
l'augmentation
que
de
de
nouveaux
phase
la
rdsulte
en
normal
c-direction
by
along the
Josephson coupling between
c-axis,
the
adjacent
between
iodine
about
the
current
and
France
forces
de
par
substitution
la
60.
jusqu'h
experimental
report
single crystals can offer
binding
new
(2)
Miiller
1994)
des
confirmd
feuillets.
c,
April
14
renforcement
est
facteur
We
Abstract.
the
P.
expdrimentaux, qui
montrent
monocristaux
plomb dans des
normale,
d'un
c
accepted
Le
phase
la
les
couplage
Josephson
entre
la
direction
importantes
dans
hystdrdtiques,
dtats,
deux
avec
of
par
substitution,
induit
entre
2
('),
Mellet
Bagneux,
Germany
92220
and
l'anisotropie.
rdduire
rdsistivitd
Bi-2
R.
Garching,
8046
revised
prdsentons
Nous
substitution
d'iode
Savary ('),
H.
Bagneux,
CNET
Februaiy
Rdsumd.
la
('),
Schneck
Telecom,
3
permettre
lead-
(2)
Walther-Meissner
(Received
in
cuprates
bismuth
R.
coupling
Josephson
and
that
the
increase
reduce
to
The
in
strengthening
induced
by
lead-substitution,
is
confirmed
the
lead-substitution
has
the
high as
the layers, resulting
hysteretic
two-state
and
lead-substitution
the
phase,
factor
a
of
anisotropy.
the
as
60.
in
I-V
In
the
high
by
effect
to
superconducting
densities
of
characteritics
critical
without
branches.
Introduction.
1.
layered
and their high degree of anisotropy it has been argued that
structure
superconductors can be described
Bi~sr~cacu~os
coupling in bismuth
cuprates
~,
bilayers with the BiO and
superconducting
CUO~
coupling
of
the
Josephson
a
corresponding to
description,
This
metallic
barriers.
acting as insulating or
Owing to
interlayer
term
of
planes
their
model
Lawrence-Doniach
length f~
coherence
picture
has
been
first
is
small
[11,
as
indirectly
is
consistent
compared to the
supported by
with
15
the
fact
that
in
this
material,
the
the
in
SrO
the
c-acis
I spacing between the CUO~ bilayers. This
investigation of
experiments
devoted
to
several
2250
JOURNAL
the
temperature
and
d-c-
dependence
angular
and
manifestations
of
intrinsic
the
PHYSIQUE
DE
of the
critical
upper
Josephson
directly that
N°
III
effect
[21.
fields
have
recently
More
observed
been
in
the
thin
II
a-c-
single
like a series
of
showing
behaves
of Bi~Sr~CaCU~O~
crystal
array
a
Josephson junctions [3].
characteristics
Finding a way to tune the anisotropy of the material and possibly change the
should
superconducting CUO~ bilayers
allow
of the
Josephson coupling
between
the
to
interlayer
concerning the
influence
of the
experimentally
investigate the important
issue
coupling on the superconducting properties.
in
increasing
lead-substitution
single crystals of
show
that
the
In
this
paper,
we
This
Bizsr~cacu~og_~
possibility
progressively
reduce
the
anisotropy.
offer
the
to
can
observations,
concerning the evolution of
conclusion
relies on a
experimental
consistent
set of
modifications
of the
perpendicular
structural
properties,
well
the
transport
some
as
as
of lead.
We particularly
emphasize this latter aspect by
properties, relatively to the
amount
of the
resistivity anisotropy, in the
normal
phase and a
showing a progressive
decrease
critical
density, in the
superconducting
increase
of the
perpendicular
progressive
current
lead-substitution
Josephson
interlayer coupling,
phase. We
discuss
the
effect
of the
the
on
modifications
characteristics
induced
observation
in the I (V)
by the
through the
of striking
for
of
possible physical
implications of these
results
and
relevance
lead.
The
presence
discussed.
applications are also
crystals
_,,
tunnel
Experimental.
2.
Our
studies
method
been
we
carried
have
been
have
previously
obtained
by changing
by
of
checked
means
composition
composition from one
fraction
the respective
approximately to Bi~
uniform
out
an
over
the
crystal
single-crystals
[41. Crystals
PbO
the
electron
of
on
described
to
the
and
and
lead
cations
the
in the
:
2
:
cations
The
diameter.
good
a
lead
phase
2
lead
differente
melt.
of I ~Lm
for each melt
Changing
another.
Bi-2
with
microprobe
surface,
bismuth
in
amount
of the
proportions
found
We
for
reproductibility
amount
in
elaborated
concentrations
the
formulas,
average
from 0 to 0.4. We
melt
in the
a
have
have
each
by
been
crystal
a
average
mainly affects
correspond
which
consistently
_,Pb,Sr~cacuzo~,
have
with x varying
bismuth
site, a type of
substitution
which is also
mainly
substituted
at the
investigations of the
consistent
with
previous
considerations
structural
[41 and with
recent
~°~Pb nuclear
BiSrCaCUO
magnetic
of
lead-substituted
compounds [5]. The good
resonance
X-ray precession
crystalline quality of our as grown crystals is attested by the observation,
on
photographs of the (hk0) and (0k/ reciprocal planes, of very well defined Bragg reflections,
result
diffused
strikes along the I * reciprocal
direction
which
would
and in particular with no
intercalation
has been
disordered
stacking of the layers constituting the crystals. Iodine
from a
evacuated
Pyrex glass ampoules, at 150 °C,
achieved
by annealing crystals and iodine in
owing to this
intercalation,
both
variations
the
during ten days. We have
measured
c-parameter
diffractometer.
We
have
circles
X-ray
photographs and with a two
X-ray precession
on
method
[6],
with the
standard
Montgomery
performed the resitivity anisotropy
measurements
3
of
thickness
between
9
and
platelets of typical
dimension
000 x 500 ~Lm~ and
~Lm
~Lm
on
0.I and lo mA at
between
depending on the sample, by using an a-c- technique with
currents
flowing along the c-axis
characteristics
with the
Josephson
I kHz.
The d-c- and
current
a-cdifferent
methods.
The
have
been
performed on crystals which have been prepared with two
obtain
thinperpendicularly
the
c-axis,
single-crystals
cleave
first one
consists to cut and
to
to
of approxithickness
dimensions
50 x 50 ~Lm~ and of
rectangular platelets of typical lateral
photolitogcombination
of
method.
technological
By
other
mately 1-3 ~Lm. The
a
a
one
uses
cylindrical
single
crystal
of
patterned
milling
have
sets
mesas
~aphy and of Ar-ion
on
we
60
and
their
thickness
30
and
varying
between
of
the
piatejets j7j the diameter
~Lm
~Lm
mesas
assumed
that
lead
is
N°
JOSEPHSON
II
varying
between
the
across
mesas
were
electrode,
lower
and
measuring
emission
Experimental
3.
STRUCTURAL
the
structural
In
that
with
the
weak
very
sufficient
x
the
upper
reference
as
details
in
electrode.
the
microwave
The
[3].
lead-
parameter
from
0.4.
0 to
0
for,;
have
We
found
as
As
of
amount
lead
described
forces
adjacent
increase
should
We
lead-free
in
between
substitution
intercalation.
in
intercalation
iodine
inter-plane binding
this
c-lattice
of the
at
com-
the
result
of a stage-I
in the
longer
intercalates
no
Bi~sr~cacu~og
is permitted by
~,,
BiO planes,
have
concluded
that
we
binding force to such a point that it
This
is
iodine
lead-substitution
that
say
can
increase
an
respectively.
figure I,
0.I
and
schematically
0.36.
~
iodine
prevents
plane
mesa
=
crystals
Josephson transport
measurements
of the single crystal platelet as
the
case
etched
In order to specify the
of
lead-substitution
consequence
compared the ability of iodine to intercalate in lead-free and
have
performed iodine
intercalation
Bi~_,Pb,Sr~cacu,O,,
in
37.61,
and
[8]. But
intercalation
a
we
crystals. We
ranging from
38.0
I.
000
have
with.r
to
7
2251
ANISOTROPY.
level,
substituted
30.8
and
performed by using the
the top of the investigated
technique is described in
BiPbSrCaCUO
IN
results.
3, I
Pounds
0001
2
COUPLING
reduces
the
«structural
anisotropy » of the BiO planes which is related to the
difference
intra-plane and
between
the
the inter-plane binding
forces.
This
conclusion
is also
consistent
with that we have previously
drawn
from X-ray
diffraction
studies [41, which
pointed-out that
lead-substitution
induces
have
the following
structural
modifications
of
decrease,
increase
the
incommen(.-parameter
a
an
modulation
wavelength and the in-phase stacking of the blocks
relatively to the
surate
incommensurate
with
the
planes,
modulation.
of
occurrence
could
which
a
have been previously
consistently
discussed
inter-plane binding forces between adjacent Bi-O
establishment
covalent
of a
type of bonding [41.
Indeed,
result
from
results
these
strengthening
of the
the
A
B14J
B14J
@
Bi-O
~
Bi-O
~c.
O~
.~
B
Fig.
;
Schematic
I.
0. I
relatively
stacked
iodine
to
and
representation
intercalates.
the
are
The
bonded.
iodine
are
c.
30.7
intercalation
out-of-phase
modulation
incommensurate
strongly
of
bloks
and
I.
cm
Iodine
37.61.
no
Bi~_,Pb,Sr~CaCU~O,. A)
weakly bonded along
in
stacked
and
B) For
longer
;
m
intercalates.
0.35,
the
For
x
bloks
0
and
=
c-direction,
the
are
in-phase
2252
3.2
JOURNAL
RESISTIVITY
The
ANISOTROPY.
plane p~ resistivities
for
in
figures
represented
are
lead-free
2
lead-substituted
Comparison
3.
N°
III
dependence
crystals,
temperature
and
and
PHYSIQUE
DE
of the
in-plane
ranging
of the
with
transition
x
p~~ and
from 0. I
for
temperatures
the
II
out-ofto
0.4,
different
pc (Ohms,cm)
50
o.75
~'
f
40
~
.
pb/B%25%
.
~
"..~
%
'
30
50
.
150
~
~
..
~
20
.
10
'..
.
o
50
T@Q
.
2.
Fig.
T~
:
(.j
-
=
Temperature
of
(v)
K.
86.6
~~Pbo
Bij
:
Bii
/P
P
=
~
K,
the
inset
vs.
p,
shows
T~
:
ead-substitution.
this
cristal
with
=
a
84
dilated
~b
~
lE7
~............
..
..
.
'..
..
.
.
.
50
lE4
~....-...
100
150
200
250
300
T@Q
.
Fig.
3.
Temperature
(.) Bi~Sr~CaCU~O~
T~
T~
79.2
K.
Note
that
dependence
86.6
each
K.
curve
of
the
resistivity
anisotropy
(v) Bij »Pbo 2~Sr2CaCu20,
differs
from
each
other
by
:
as
T~
one
a
function
84 K.
order
of
of
the
lead-substitution.
(m) Bij ~Pbo ~Sr~CaCU~O,.
magnitude.
N°
JOSEPHSON
it
COUPLING
IN
BiPbSrCaCUO
2253
reduction
from
approximately 88 K to 80 K, as
lead
amount
measure
as the
crystals. It is shown in figure 2, that increasing the
of
lead in the
amount
crystals induces a progressive decrease of the room
magnitude of the out-of-plane
temperature
resistivity p,, of approximately a factor 25, from 20 n-cm to 0.8 Q-cm- Near T~, the decrease
of p~ corresponds to approximately
order of magnitude for
intermediate
lead
concentration
one
0.25
factor
60
and
reaches
the
optimum
of
lead-substitution
This is
0.4.
at
x=
a
xi
accompanied by a progressive
modification
of the
semiconducting
of
type
temperature
dependence (dp,/dT
0 ), which has been previously reported in
lead-free
crystals [91, toward
quasi-metallic
of
behaviour.
Actually,
for
the
optimum of
lead-substitution,
type
a
decreases
linearly
with
decreasing
down
130
around
K
where
it presents
temperature
to
p,
a
shallow
minimum
and
then
increases
slightly until T~, where it drops abruptly.
The
dependences of the anisotropy p~/p~~, for crystals with different
of lead
temperature
amounts
substitution,
figure
represented
in
3.
It
clearly
in
the
whole
temperature
are
appears,
range
between
and the
superconducting
transition,
lead-substituted
that
crystals
temperature
room
have a
weaker
resistivity anisotropy than the
lead-free
This
decrease
of anisotropy
ones.
mainly results from the progressive increase of the out-of-plane conductivity, as
measure
as the
of
lead-substitution
increases
in the samples. For
intermediate
lead-concentrations,
the
amount
resistivity anisotropy is one order of magnitude lower than that of lead-free samples. And for
the
optimum of
lead-substitution,
this
decrease
of the
anisotropy is up to two
orders
of
Consistently,
modifications
magnitude
weaker.
have
observed
significant
resulting
not
we
from the lead
addition
in the
magnitude and in the
behaviour
of the
in-plane
temperature
resistivity p~~.
samples yields
increases
in
a
T~
the
~
I-e- with each CUO~ bilayers
layers
acting as a the barrier,
as
have
been
observed
and
described
in the
Bi-2 : 2
lead-free
2
single
crystals [31. We show
:
that the Josephson
effects
lead-substituted
along the c-direction, still exist in the
crystals but
with
characteristics
consistent
with a strengthening of the interlayer coupling. We present here
typical
manifestations
of the
intrinsic
obtained
Josephson effect,
for the
heavily
most
some
substituted
crystals (~
0.4
the
existence
of hysteretic I-V
characteristics,
when the
current
flows along the
microwave
emission
c-axis
(see Fig. 4) and
(see Fig. 5). The I(V)
curves
checked
that
exhibit
branches,
superconducting
and
resistive
We
have
the
two
a
one
a
one.
voltage jump, corresponding to the switching from the superconducting branch to the resistive
with an
increase
of
thickness
This
result is
consistent
is proportional
of the crystals.
to the
one,
crystals, if we
the
crystals
the
number
of junctions
with
the
thickness
of the
suppose
microwave
of
identical
junctions. The following
results
of
constituted
with a
series
array
emission
emission
confirms
this assumption.
The
detector
set-up we have used has its range of
operation
junction and according to the
frequency-voltage
around
lo GHz.
For a Single
emission
should
Josephson relation, Josephson
in this frequency
correspond to a voltage
range
of only few tens of
microvolts
observe
emission
coming
the junction. In
to
across
consequence
from
crystal,
have
performed
the
72K,
temperature
measurement
at
a
we
near
a
74 K)
the
characteristic
where
voltage of the I(V)
is strongly
decreased.
curve
T~ (T~
Figure 5 shows the
microwave
emission
detected
GHz.
observe
I1.05
We
rather
at f
a
broad
emission
because
such
high
all junctions
within
crystal radiate
at
temperature
a
a
incoherently.
=16.8
The
peak
maximum
arises
Hence,
relation
V
mV.
the
Josephson
at
f
2 eV/hN
allows
of
calculate
the
number
N
radiating
junctions
in
series
For
to
us
a
array.
the
consideration,
this
gives
N
740
junctions
under
with
voltage
of
22
~LV per
case
a
lsi,
junction.
Multiplying
the
number
by
I-eN
the
spacing
between
consecutive
CUO~ bilayers, we obtain I. ~Lm, which is roughly the thickness of the sample measured
with
scanning
microscope.
electron
a
3.3
JOSEPHSON
acting
the
couPLiNG.
superconducting
The
intrinsic
electrode
and
Josephson
the
BiO
effects,
SrO
and
=
=
=
=
=
2254
JOURNAL
PHYSIQUE
DE
III
N°
o.i
o.05
'i'
f
0
<
=70
'~
.o.05
-o.i
.i
-o.5
o
Fig.
4.
hysteresis
80 mV,
for
characteristics
I-V
different
two
Note
temperatures.
is
Outside
maximum.
which
crystal
with
there
that
lead-substitution.
maximum
a
only
is
characteristic
relatively
remains
a
o.5
(volts)
v
branche~.
two
70 K,
at
Inside
74
T~ (T~
near
Bij ~Pbo ~Sr~CaCU~O,.
for
4 K,
the
characteristic
K),
at
the
T
=
of R~
value
I~ is of
high.
0.0045
I
~
~-
0.0035
E
G~
f
5
<
0.0025
~
f
-0.025
n
o.ooi 5
-o.05
-o.i
-o.05
Fig.
5.
I-V
characteristic
maximum
arises
at
place,
corresponding
in
as
grown
mV
when
not
characteristics
have
observed
at
two
out-of-plane
we
increase by nearly two
to an
crystals [3, 10].
lead-free
have
found
for
values
4.2K
of
important
critical
orders
crystal
a
with
substracted),
been
voltage
the
o.i
(vi
emission
have
=
Comparing the I(V)
samples we
first
microwave
resistances
16.8
V
substituted
the
and
4Sr~CaCu~O~ (contact
B ii ~Pbo
o.05
o
v
are
as
corrected
grown
magnitude
of
=
the
the
as
and
lead
lead-substitution.
In
high
respect
peak
resistances.
contact
samples
lead-free
with
76 K ). The
74 K (T~
from
densities
lead-substitution,
maximum
a
=
consequences
current
of
at T
as
to
5
000
reported
A/cm~,
values
N°
JOSEPHSON
II
second
In the
effective
(V
I
place, the I (V )
curves,
junction (see Fig. 4),
»
do
curves
not
show
the
COUPLING
large
seem
with
a
specific
number
of
two
of
IN
branches
the
branches
2255
BiPbSrCaCUO
characteristic,
lead-substituted
whose
existence
similar
samples.
has
been
to
a
«
Indeed,
single
these
reported in
single crystals. Such
branches
been
interpreted [3] as the result of a
has
switching from the superconducting to the resistive state, of the slightly different
behaviour
junctions stacked in the crystals. We have carefully checked that the distinct
does
technological process of preparation of the samples
result
from an unexpected
effect of our
not
with multiple
branches, for samples prepared
[7], by verifying the persistence off (V
curves
lead-free
crystals.
in the
with
manner
same
lead-free
the
succession
4.
of
Discussion.
peculiar
intrinsic
Josephson effect in
lead-substituted
samples can be
described
anisotropy
particular the
above.
In
decrease
of
lead-substitution
is fully
consistent
with the
observation
of a higher
critical
current
p, with
density in the arrays of junctions, since it is known that in Josephson junction (of the SIS or
SNS types), the
critical
density is proportional to the inverse of the normal
current
state
[10].
Hence,
this
resistance
decrease
of p~ implies a strengthening of the inter-layer
Josephson
coupling and an
of the Josephson
tunneling.
enhancement
the
We
believe
of multiple
branching in the I(V)
of the
lead-substituted
absence
curves
samples to be due to a less sensitivity of this system, with respect to the lead-free
to the
one,
spreading of the parameters of the junctions,
results
from the
disorder
which
structural
of the
lead-free
crystals.
Indeed
of the
multiple branching in
the
crystals has been
occurence
interpreted [3] as the result of a succession of switching from the superconducting state, of the
lead-substituted
slightly different junctions staked in the crystals. In the
the
greater
case
is
tolerance
these
slight
differences
possibly
related
important
problem
of the
the
to
to
«
»
interaction
junctions [[[J. In
lead-substituted
effective
interaction
between
samples, a more
which has the effect that the switching of one junction to the
resistive
drive
state,
may
occur,
the global switching of the entire
This
triggering
of
the
switching
of
global
the
array by a
array.
single junction, could be assigned to a modification
leading
of the
in the barrier,
conductance
effective
dynamic
higher
conductivity
coupling
of
the
junctions.
Indeed,
of the
the
to a
more
barrier
resistive
resistive
load of
could play the role of a
matched
load,
similar
extemal
to the
electronic
circuits,
which
the
in-phase locking of the Josephson
is
known
stabilize
to
identical
junctions [12].
oscillation
in
artificial
of slightly
non
arrays
lead-substituted
coupling along c in the
compound is not
efficient
The origin of the
more
properties of the
electronics
clear at present.
This origin has to be found in the changes in the
between
valence
difference
the
material
which
certainly result from the two following factors
lead-substitution.
The
modifications
induced by
valence
lead and
bismuth,
and the
structural
mechanisms
difference
between
lead and
bismuth
might be compensated by several types of
from
BiO
planes or
including hole doping of the CUO~ planes,
departure
the
oxygen
and
of Pb~ + with Pb~ +
therrnoelectric
coexistence
Indeed,
measurements
recent
some
power
'~O NMR
lead-substituted
of hole doping in
investigations
support the
to
occurrence
seem
qualitative
would
existence
of
similar
materials
[13]. This
give consistency to the
some
features, to those reported here, in oxygen
lead-free
annealed
crystals [14], a treatment
which
similarities
include
is known
increase
hole
concentration
This
the
the
in
the
CUO~
planes.
to
[16],
the
increase
of
the
out-of-plane
reduction
[15],
the
shrinking
of
the
c-parameter
T~
density [3]. However it is
[3, 15] and the
increase
of the
c-axis
critical
conductance
current
important to note that, while the magnitude of the T~ reduction is the same in lead-doped
annealed
crystals, the amplitude of the decrease of anisotropy
crystals than in lead-free
oxygen
lead-substituted
in the
properties
significantly
samples.
is
important in
transport
more
The
related
to
characteristics
the
decrease
of the
of
2256
PHYSIQUE
DE
JOURNAL
N°
III
II
suppression of the multiple branching in the I (V
has only been
observed
curves
samples. Consistently with these
considerations,
exclude
cannot
we
that, besides hole doping of the CUO~ planes, specific effects resulting from
lead-substitution
emphasize the
of the
could
and
effective
decrease
anisotropy with respect to what
occur
properties of the leadhappens in oxygen
annealed
electronic
samples. We can think to the
creation
substituted
BiO planes,
metallic
semiconducting,
of an impurity
the
suggest
or
or
band at the Fermi
level in these planes. We can also
consider
of the
the possible
consequences
modifications
described
above
and
interpreted
induced
by
have
the
structural
occurence,
we
as
instance,
lead-substitution,
of
bonding
between
BiO
For
such
the
of a
covalent
planes.
type
a
bonding could permit both an increase of the carriers density and an overlap of the outer
shells of the atoms
involved
in this bond to a
sufficient
compatible to
electronic
that are
extent,
increase
of conductivity
the
along the c-axis. Owing to these
unsolved
questions it is not
possible to
discriminate
whether
the T~
modifications
by
lead-substitution
at the
present time
only results from hole doping or also from the
decrease
of anisotropy.
Although experimental
clarifications
needed
specify the role of
lead-substitution
to
are
on
believe
the
electronic
properties of the material,
of
efficient
that
the
origin
the
we
more
coupling along c, could be due to the
effect, resulting from an
of a proximity
occurrence
increase
carrier
of the
density, induced by the
lead-substitution,
in the
barrier-layers ». In the
norrnal
modification
carrier
phase, this
in the
density should be related to the
increase
of
conductance.
In the
superconducting
will
extend
phase, a proximity
effect
the
of
range
coherence
superconducting
along c and determine a higher critical
[17]. The
existence
current
of proximity
effect
has been
often
invoked
favour
coupling
mechanisms
between
closely
to
junctions [11], and
consequently
be
considered
spaced Josephson
could
also
in
the
improvement of the dynamic coupling between the elementary junctions of
lead-substituted
crystals.
Besides
implications of
these possible physical
lead-substitution,
results
relevant
present
our
electronics.
In the first place,
aspects for applications in latching logic and in high frequency
Moreover
in
the
lead-substituted
the
«
obtained
can
we
the
to
of
number
great
R~I~
hysteretic I (V ) characteristics,
free of branching. In the
second
voltage jump in the I-V
characteristics
high
represents
very
a
mV at 4 K, see Fig. 4) owing to the
addition of the
characteristic
voltages of
of
junctions
constituting
the
intrinsic
series
This
allows
to
array.
high as
80mV
70K,
I-e74K).
Furthermore,
the
at
as
near
T~ (T~
two
«
place, the value
R~ I~ product1660
remain
states
»
the
=
enhancement
locking
phase
increase
~5.
We
of
for
the
output
have
of
power
the
It
junctions
may offer the possibility to
result
from
this phase locking,
should
emitted
the
of
of
allow
Bi-2
2
studies
to
lead-substitution
that
shown
superconducting
through the d-ccould
coupling between
all the junctions.
radiation
and
mutual
a
considerable
[I II-
bandwidth
narrower
a
have
a
Conclusion.
anisotropy
result
of the
:
about
the
phase,
and
have
we
have
intrinsic
a-ca
structural
«
material
also
anisotropy
observed
Josephson
with
an
possibility
the
compounds.
lead-free
2
offer
can
effects.
intermediate
the
In
»
and
to
normal
the
consequences
We find that
behaviour,
decrease
the
phase,
resistivity
of
this
this
between
this
extremely high
conclusion
anisotropy.
anisotropy
is
In
case
the
decrease
lead-substituted
the
the
of the
cuprate
lead-
model, and a 3D case,
Lawrence-Doniach
pictured by the 2D
free Bi-2
2
framework.
YBaCUO
might correspond to
Ginzburg-Landau
anisotropic
within
describable
an
observations
intrinsic
the
Josephson
effects
in
However,
interpret
this
latter
to
on
our
case.
which
take
effectively
develop
the
models
materials, it could be
lead-substituted
to
necessary
2,
into
account
which
proximity
is well
effects
[17].
N°
COUPLING
JOSEPHSON
2257
BiPbSrCaCUO
IN
References
II
12th
Kyoto,
L.
N.,
Silva
E.,
Bulaevskii
S.,
Doniach
and
Theory
«
Conference
International
Japan,
[2]
E.
W.
Lawrence
1971)
Layer
of
Low
on
Superconductors
Physics, E. Kanda Ed.
Structure
temperature
»,
Proceeding of the
(Academic Press of
361.
p.
Macroscopical
Theory
Layered
of
Superconductors,
Int.
Phys.
Mod.
J.
B 4
(1990)
1849
S.,
Sarti
Fastampa R., Giura M,
Temperature
Marcon
and
B12Sr2CaCu~Og_,.
in
Experimental Study of
Dependence, Phys.
R.,
Magnetic
and
the
Field
Rev.
Dimensionality
B 49 (1994)
556.
[31
Steinmeyer F.,
R.,
Single Crystals, Phys.
Kleiner
R.
Miiller
and
(1994)
49
[41
L.,
Pierre
[71
[81
[91
[101
[I ii
[12]
ii 3]
Miiller
and
G.
Lent.
68
j1992)
Josephson
Intrinsic
P.,
J.,
Schneck
D.,
Morin
in
P.,
Intrinsic
Josephson
Effects
Bi~srjcacu~og
in
2394
Effects
in
High-T~
Phys.
Superconductors,
Rev.
B
Tolddano
Production
the
J., Daguet
Superconducting
J. C.,
Primot
l10-K
of
and
Savary H.,
Single
Phase
C.
Role
Lead-
of
Bi-Sr-Ca-Cu-O
Phys. 65 (1990) 2296.
Supraconducteurs h Haute
Oxydes
Tempdrature Critique
BiSrCaCUO
par
Rdsonance
Nucldaire,
thesis,
Universitd
Magndtique
de Paris VI (1993).
Electrical
Resistivity of Anisotropic Materials, J. App/.
Montgomery H. C., Method for Measuring
Physic-s 42 (1971) 2971.
Rdgi F.-X.,
Schneck J.,
Palmier
J.-F. and Savary H., 70 K High R~ I~ Hysteretic
Josephson Effect
Lead-Substituted
Single Crystals of Bi~Sr2CaCu20~, to be published in J.
in Mesas
Pattemed
on
(October1994).
App/. Phys.
Gronski
Xiang X. D.,
Vareka
Zettl
A.,
Corkill
Cohen
R.,
W.
A.,
J. L.,
L., Kijima N. and
Metallization
Intercalation,
Phys.
of the Resistivity
Tensor in Bi~Sr~CaCU~O, through Epitaxial
Rev. Lent. 68 (1992) 530.
S.. Fiory A. T., Fleming R. M., Espinosa G. P. and Cooper A. S., Anisotropic
Critical
Martin
Current
Density in Superconducting B12Sr~CaCu~Og Crystals, App/. Phys. Lent. 54 (1992) 72.
Likharev
K. K.,
Superconducting
Weak
Links,
Phys. 51 (1979) 101.
Ret,.
Modern
Likharev
Mutual
Phase
lain A. K.,
Locking in Josephson
K. K.,
Lukens J. E. and Sauvageau J. E.,
Junction
Arrays, Phys. Rep. 109 (1984) 309.
Wiesenfeld
K., Phase Locking of Josephson-Junction
Series
Arrays,
Hadiey P., Beasley M. R. and
Phys. Rev. B 38 (1988) 8712
Josephson-Junction
Array Variation,
between
Wiesenfeld
K., On the Comparison
Tsang K. Y. and
1075.
J. App/. Phys. 70 (1991j
Carrington A., Ayache C., Le Noc L., Trokiner A., Schneck J. and Pougnet A. M., « Doping level
thermoelectric
and
local
between
in Bi
based
(n
1, 2, 3) cuprates : a comparison
power
M~S-HTSC-IV
conference
(5-6 July 1994,
International
susceptibility »,
Submitted
the
at
Ceramics,
[61
Rev.
1327.
Substitution
[51
Kunkel
Kleiner
Le
L.,
Noc
App/.
J.
Etude
des
=
Grenoble,
[14]
Hsu
Mitzi
W.,
J.
distortions
France).
D. B.,
the
in
Kapitulnik
resistive
K.
A.
and
of
transitions
Lee M., In-plane dissipation
oxygen-doped B12Sr~CaCu20g
maxima
and
vortex-line
single crystals,
Phys.
_,,
Lent.
Ret>.
[15]
[161
T.,
Takano
resistivity
in
Yasuda
Y.,
Deshimaru
the
2095.
and
S.
Theodorakis
Rinderer
Bijsr~ca-Cujog_,,
Otani
T.,
superconductivity
(1991)
II?]
(1991)
67
of
Effects
Physiia
Y.,
Shimizu
L.,
Bi-based
Miura
oxides
C
N.
non-stoichiometry
of
oxygen
208
(1993)
and
Yamazoe
homologous
on
the
anisotropic
385.
to
N.,
Influence
2212
phase,
of
Japn
oxygen
J.
content
Appl. Phys.
on
30
L1798.
S.
Physic-a C
and
190
Feinberg
(1992)
271.
D.,
Field-Independent
Anisotropy
in
Layered
Superconductors,