- Email: [email protected]
The Meissner effect of polysulfur nitride, (SN)x
Solid State Communications, Vol. 32, PP. 659—663. Pergamon Press Ltd. 1979. Printed in Great Britain.
THE MEISSNER EFFECT OF POLYSULFUR NITRIDE, (SN)~ Y. Oda, H. Takenaka, H. Nagano and I. Nakada The Institute for Solid State Physics, The University of Tokyo, Roppongi, Minato-ku, Tokyo, Japan (Received 1 June 1979 by W. Sasaki) The magnetic susceptibility of (SN)~was measured by the a.c. method. The Meissner effect occurs at 250 ±3 mK. The real part of the susceptibility nearly saturates at 100 rnK and reaches 93 ±7% of I /41r at 30 mK for weak field perpendicular to the polymer axis, while for the parallel direction it remains at 65 ±10% of 1/4ir. The susceptibility depends strongly on the ac. magnetic field. There is a peak in the imaginary part of the susceptibility at the transition region to the superconducting state. —
—
SINCE the discovery of superconductivity of polysulfur nitride, (SN)~[11,a large number of investigations were reported. To date studies of superconductivity in (SN)~ consist chiefly of measurements based on the electrical resistance [1—5] Only recently the observations of the Meissner effect were reported [6,7] However, the perfect diamagnetism of (SN)~was not defmitely confirmed. Previous works suggest that (SN)~is a type II superconductor with high H~2and extremely low .
-
H~1[3]. Still the fundamental mechanism for the occurrence of such a particular behavior of superconductivity of (SN)~has not been cleared. In this communication we report the results of experiments concerning the Meissner effect performed to confirm the perfect diamagnetism of (SN)~which is essential to the study of the fundamental mechanism of superconductivity, The crystals were grown by the method similar to that reported by MacDiarmid et al. [81 In order to grow larger and high quality crystals both for better sensitivity and reproducibility of the measurements, we made two modifications to the crystal growing technique. First, the cold finger was kept to about 50°Cto trap S2N2 selectively. Secondly, at the time of the transport of S2N2 to the crystal growing chamber, the wall of the chamber was cooled locally by a point contact of a heat pipe. With this method we could grow several larger crystals successfully. We measured three sets of specimens. Among them, each of the two sets consisted of two pieces of single crystals mounted in the same crystallographic orientation. The masses of the sets were 31.8 and 33.1 mg. The third was a piece of single crystal cut into a shape of cylinder with the cylindrical axis parallel to the crystal b-axis. The ratio of height to diameter was approximately one. The mass was 33.3 mg. All of the data reported here were obtained using a
dilution refrigerator to cool the specimens. The temperature was measured by two carbon resistors attached to the mixing chamber of the refrigerator. The resistors were calibrated by CMN thermometer and NBS’s SRM 767 [9J.The accuracy of the calibration is better than 1% [10, 11] .The specimen was mounted and cooled in a bundle of insulated thin copper wires. The one end of the bundle was attached to the mixing chamber. The crystal was greased with an apiezon-N to keep good thermal contact. The magnetic field H at the sample was applied by means of a solenoid wound on the 1 K thermal shield of the refrigerator and could be represented as H = Hd~+ H~ cos (2irft) + where ~ and HLC. were a d.c. and ac. magnetic field respectively, applied in the same direction, z~ was a total residual field,f was a frequency and t was a time. As the superconductivity of (SN)~was quite sensitive to magnetic field, the residual field which was produced by the earth and other sources was reduced by magnetic shieldings to less than 5 mOe. The magnitude was low enough in our measurements to affect the results. The magnetic susceptibility was measured with a standard ac. bridge method [10—121 By the a.c. measurement the susceptibility is represented as x = x’ ix”. With the known coil geometry, absolute values of both the real (x’) and the imaginary (k”) parts could be deduced. The measurements were made at frequencies of 18, 35, 70 and 280 Hz. In order to determine the susceptibility quantitatively it is necessary to correct the effect of demagnetizing field The relation between true (Xo) and apparent (x) susceptibility is expressed as x = xol (1 v), where p is a demagnetizing factor. As it was difficult for (SN)~to determine p from the geometry, we had mounted together with an (SN)~crystal a piece of Sn—Pb alloy cut into a similar form in the same ~,
-
—
-
—
-
—
659
660
THE MEISSNER EFFECT OF POLYSULFUR NITRIDE, (SN)~ I
I
I
I
X .L b axs
a +
Hac 0.017 0.034 0.068 0.14
Oe Oe Oe Oe
•
0.23
Oe
a a
0.34 Oe
• o
f~70Hz
HDC~0
1.0 __
0
eSeS~
‘0
• •~ ~• e . so,,
8 0
>.
a
a
0.68 Oe
1
a a
Vol. 32, No.8
a a a
a
+
0.
~
a a
.
$
a
ae. a
A~
0
~
0
a a
0
50
100
150
200
250
I (mK)
Fig. 1. Temperature dependence of the real part of the susceptibility for various a.c. magnetic fields. HLC. is the amplitude of measuring field applied perpendicular to the crystal b-axis.
x’/Ib
HAC
axis
• 0.017 Oe 0 0.034 Oe a 0.34 Oe 0 0.68 Oe fa7OHz Hoc:O
a6
00’O~
0S 0,. 0
• 0~
a
S
a
0 0
0•
a
0
a
a0
. 0
a
0
0
•.
0a
50
100
150
•
0
a~
A° 200
A
oOo.a.A0
250
I (mK)
Fig. 2. Temperature dependence of the real part of the susceptibility for various a.c. magnetic fields. ~ to the crystal b-axis. orientation as a standard for calibration. The Sn—Pb alloy transformed to the superconducting state at 7.5 K. Below the transition temperature the alloy is in the perfect diamagnetic state and xo is l/4ir. In the normal state the a.c. field penetrates the alloy sufficiently as the skin depth is large enough compared to the size of the specimen. Since the demagnetizing effect is taken to be similar to either the alloy or (SN)~,we can obtain the true susceptibility of (SN)~with the standard procedure by correcting the volume difference between the two. —
is parallel
We observed no frequency dependence. This means that the eddy current heating by a.c. magnetic field was negligible. The shielding effect in the normal state could also be neglected. Moreover, no hysteresis in the susceptibility was observed with either field or temperature sweeps. For three sets of specimens mentioned above we obtained nearly identical results in magnitude and the behavior of susceptibility. This may be an indication that the crystals prepared were uniform in quality. In this paper signs of II and .1. indicate the parallel
THE MEISSNER EFFECT OF POLYSULFUR NITRIDE, (SN)~
Vol. 32, No. 8
661
xjb axis (normaLized) 1.(
D
aD a
N
a
a
D
D
34mK
a
63mK l9lmK
0
f:7OHz HDCOO
a 0
C
a
D
—
—I
~0.5
a 0 A 0
D
a 0 0 0 00 0
0
0.2
0
0:6 HAC(Oe)
Fig. 3.H dependence of the susceptibifity for various temperatures. All the data are normalized at ~ is perpen’dicular to the b-axis.
=
~.
I
I
X~jb axis
g
a
a
I
0. HLC
I
(normalized) a
a
34mK 63mK ol9lmK a
~
0 0
70 Hz HACaO.034 Oe 0 0 0 0
I
0
0.5
1.0
I
I
I
1.5
2.0
2.5
3.0
HDC (Oe)
Fig. 4. HdC dependence of the susceptibility for various temperatures. HLC is fixed at 0.034 Oe HLc and HdC are -
applied in the same direction perpendicular to the b-axis. The data are normalized at HdC. and the perpendicular direction to the b-axis respectively. The measurements throughout the plane normal to the b-axis are not specially distinguished since (SN)~ is isotropic magnetically as reported by Azevedo eta!. [3] This was also re-examined in our experiment, The temperature dependence of x~at Hd.c = 0 is shown in Fig. 1. With decrease of temperature for HLC <0.0340e, x~ increases rapidly at first and then the change becomes quite gradual and nearly saturates .
=
0.
at about 100 mK. From the comparison with the change of susceptibility of the Sn—Pb alloy, we have obtained for (SN)~a susceptibility (xe)) of 93 ±7% of 1 /4ir at 30 mK. It is concluded that (SN)~is essentially in the perfect diamagnetic state in this temperature region when the weak field is applied perpendicular to the b-axis. For each magnitude of a.c. magnetic field, it is possible to find a temperature T~,at which the —
THE MEISSNER EFFECT OF POLYSULFUR NITRIDE, (SN)~
662
X’l b f7OHz
Vol. 32, No. 8
axis
HDCOO
HACOO,680e
5 C
0
>.
0
0
23 00
a
L
0
0
00
0
.0 0 0
0
50
100 I
150 (mK)
200
0p
•.g~
250
Fig. 5. A typical example of the temperature dependence of the imaginary part of the susceptibility. HLC. is applied perpendicular to the b-axis with amplitude of 0.68 Oe at 70Hz. susceptibility curve begins to rise from the horizontal axis. We define T~as a superconducting transition temperature. For (SN)~,both T~and x~depend markedly on Hac. When the field is higher than 0.34 Oe we can expect no more saturation for x~ even below 5OmK. With increase of magnetic field, T~shifts towards lower temperatures and the rise of x~with the reducing temperature becomes more gradual. The temperature dependence of X~iat HdC = 0 is shown in Fig. 2. With decrease of temperature for ~ <0.0340e, x~tends to the saturation below 50mK. From the calibration with the standard specimen of Sn—Pb alloy, it is deduced that the susceptibility (Xo) at 30 mK is 65 ±10% of l/4ir. This means that some fractionsof the magnetic flux penetrate into the crystal even at low enough temperatures when the field is parallel to the b-axis, As is seen in Fig. 2, the rise of x~with temperature is more gradual than x~shown in Fig. 1. Though the determination of T 4~from X~Iincludes some ambiguity, it could be concluded that T0 from ~ coincides with that from x’~at the same magnitude ofHac. In the limit HLC 0 at Hd~= 0, T~= 250 ±3 mK for both Xi and X~i~ Figures 3 and 4 show the dependence of xi on H,,.~ and Hdc respectively. xi at 191 mK depends notably Ofl Hac and HdC. The feature is particular for HLC. Such a tendency is seen to occur at a region where the magnitude of xi changes sensitively with temperature The dependence of xi on HLC, becomes less marked and that on HdC is negligible at temperatures where the susceptibility nearly saturates. The changes of x~with HLC and HdC are similar to x —
-~
-
~.
The imaginary part of the susceptibility (x”) is related with the energy loss of the a.c. field. In the normal state, the resistivity of (SN)~is not so small and the loss by the eddy current can be neglected. In the transition region, the loss will increase due to the reduction of the electrical resistance. With further lowering of temperature the loss decreases again due to the increase of Meissner region. At the perfect diamagnetic state the loss vanishes. As a whole there appears a peak in x” as temperature sweeps. An example of x~at Hac = 0.68 Oe is shown in Fig. 5. The peak of x” at about 100 mK will correspond to the maximum loss. At the peak it is found that ix~Ix~ = 0.47. It is found that x” depends markedly on Hac. With the decrease of Hac, x” decreases rapidly and the peak shifts towards the higher temperature region. For example, at Hac = 0.017 Oe, the peak of~~ moves to about 200 mK where I x~Ix~ = 0.04. This means that the loss due to the a.c. magnetic field increases rapidly with increase 0fHLC, and the occurrence of the Meissner effect is strongly suppressed. In conclusion, we have found the almost perfect diamagnetism of (SN)~for weak field in the perpendicular direction to the molecular chain and not perfect diamagnetism in the parallel direction. The range of transition temperature is very wide. Similar temperature dependence has been observed in superconductivity of fine particles whose dimensions are less than the coherence length [13], though the absolute value of the susceptibility does not coincide quantitatively. A remarkable dependence of the susceptibility of (SN)~ on Hac has never been observed in ordinary superconductors. These phenomena seem to be explained by considering the one dimensional structure of (SN)~.
Vol. 32, No.8
THE MEISSNER EFFECT OF POLYSULFUR NITRIDE, (SN)~
The details of the study, as well as those of x” and other electrical properties, wifi be reported in the near future. Acknowledgement The authors thank Dr. S. Tamura for his helpful instruction in the measurement of the specific gravity of (SN)~. —
REFERENCES 1.
R.L. Greene, G.B. Street & L.J. Suter,Phys. Rev. Lett. 34, 577 (1975). 2. R.L. Greene & G.B. Street,1~oc.ofNA TO-ASI on Chemist,y and Physics ofOne-Dimensional Metals, (Edited by H.J. Keller), r~.167. Plenum Press, New York (1977). 3. L.J. Azevedo, W.G. Clark, G. Deutscher, R.L. Greene, G.B. Street & L.J. Suter, Solid State Commun. 19, 197 (1976). 4. R.L. Civiak, C. Elbaum, W. Junker, C. Gouch, H.!. Kao, LF. Nicholas & M.M. Labes, Solid State Commun. 18. 1205 (1976~.
663
R.L. Civiak, C. Elbaum, L.F. Nicholas, H.I. Kao & M.M. Labes, Phys. Rev. B14, 5413 (1976). 6. R.H. Dee, A.J. Berlinsky, J.F. Carolan, E. Klein, N.J. Stone,22, B.G. & G.B. Street, Solid State Commun. 303Turrell (1977). 7. R.H. Dee, D.H. Dollard, B.G. Turrell & J.F. Carolan, Solid State Commun. 24,469 (1977). 8. C.M. Mikuiski, PJ. Russo, M.S. Saran, A.G. MacDiarmid, A.F. Garito & A.J. Heeger, J. Amer. Chem. Soc. 97, 6358 (1975). 9. J.F. Schooley, R.J. Soulen, Jr. & G.A. Evans, Jr., 5.
10. 11. 12.
13.
NBS Special Publication 260-44(1972).
Y. Oda, G. Fujii & H. Nagano, Ciyogenics 14, 84 (1974). Y. Oda, G. Fujii & H. Nagano, Cryogenics 18, 73 (1978). W.R. Abel, A.C. Anderson & J.C. Wheatley, Rev. Sci. Instrum. 35, 444(1964). T. Takahara, S. Kobayashi& W. Sasaki,J. Phys. Soc. Japan 32, 1668 (1972).
THE MEISSNER EFFECT OF POLYSULFUR NITRIDE, (SN)~ Y. Oda, H. Takenaka, H. Nagano and I. Nakada The Institute for Solid State Physics, The University of Tokyo, Roppongi, Minato-ku, Tokyo, Japan (Received 1 June 1979 by W. Sasaki) The magnetic susceptibility of (SN)~was measured by the a.c. method. The Meissner effect occurs at 250 ±3 mK. The real part of the susceptibility nearly saturates at 100 rnK and reaches 93 ±7% of I /41r at 30 mK for weak field perpendicular to the polymer axis, while for the parallel direction it remains at 65 ±10% of 1/4ir. The susceptibility depends strongly on the ac. magnetic field. There is a peak in the imaginary part of the susceptibility at the transition region to the superconducting state. —
—
SINCE the discovery of superconductivity of polysulfur nitride, (SN)~[11,a large number of investigations were reported. To date studies of superconductivity in (SN)~ consist chiefly of measurements based on the electrical resistance [1—5] Only recently the observations of the Meissner effect were reported [6,7] However, the perfect diamagnetism of (SN)~was not defmitely confirmed. Previous works suggest that (SN)~is a type II superconductor with high H~2and extremely low .
-
H~1[3]. Still the fundamental mechanism for the occurrence of such a particular behavior of superconductivity of (SN)~has not been cleared. In this communication we report the results of experiments concerning the Meissner effect performed to confirm the perfect diamagnetism of (SN)~which is essential to the study of the fundamental mechanism of superconductivity, The crystals were grown by the method similar to that reported by MacDiarmid et al. [81 In order to grow larger and high quality crystals both for better sensitivity and reproducibility of the measurements, we made two modifications to the crystal growing technique. First, the cold finger was kept to about 50°Cto trap S2N2 selectively. Secondly, at the time of the transport of S2N2 to the crystal growing chamber, the wall of the chamber was cooled locally by a point contact of a heat pipe. With this method we could grow several larger crystals successfully. We measured three sets of specimens. Among them, each of the two sets consisted of two pieces of single crystals mounted in the same crystallographic orientation. The masses of the sets were 31.8 and 33.1 mg. The third was a piece of single crystal cut into a shape of cylinder with the cylindrical axis parallel to the crystal b-axis. The ratio of height to diameter was approximately one. The mass was 33.3 mg. All of the data reported here were obtained using a
dilution refrigerator to cool the specimens. The temperature was measured by two carbon resistors attached to the mixing chamber of the refrigerator. The resistors were calibrated by CMN thermometer and NBS’s SRM 767 [9J.The accuracy of the calibration is better than 1% [10, 11] .The specimen was mounted and cooled in a bundle of insulated thin copper wires. The one end of the bundle was attached to the mixing chamber. The crystal was greased with an apiezon-N to keep good thermal contact. The magnetic field H at the sample was applied by means of a solenoid wound on the 1 K thermal shield of the refrigerator and could be represented as H = Hd~+ H~ cos (2irft) + where ~ and HLC. were a d.c. and ac. magnetic field respectively, applied in the same direction, z~ was a total residual field,f was a frequency and t was a time. As the superconductivity of (SN)~was quite sensitive to magnetic field, the residual field which was produced by the earth and other sources was reduced by magnetic shieldings to less than 5 mOe. The magnitude was low enough in our measurements to affect the results. The magnetic susceptibility was measured with a standard ac. bridge method [10—121 By the a.c. measurement the susceptibility is represented as x = x’ ix”. With the known coil geometry, absolute values of both the real (x’) and the imaginary (k”) parts could be deduced. The measurements were made at frequencies of 18, 35, 70 and 280 Hz. In order to determine the susceptibility quantitatively it is necessary to correct the effect of demagnetizing field The relation between true (Xo) and apparent (x) susceptibility is expressed as x = xol (1 v), where p is a demagnetizing factor. As it was difficult for (SN)~to determine p from the geometry, we had mounted together with an (SN)~crystal a piece of Sn—Pb alloy cut into a similar form in the same ~,
-
—
-
—
-
—
659
660
THE MEISSNER EFFECT OF POLYSULFUR NITRIDE, (SN)~ I
I
I
I
X .L b axs
a +
Hac 0.017 0.034 0.068 0.14
Oe Oe Oe Oe
•
0.23
Oe
a a
0.34 Oe
• o
f~70Hz
HDC~0
1.0 __
0
eSeS~
‘0
• •~ ~• e . so,,
8 0
>.
a
a
0.68 Oe
1
a a
Vol. 32, No.8
a a a
a
+
0.
~
a a
.
$
a
ae. a
A~
0
~
0
a a
0
50
100
150
200
250
I (mK)
Fig. 1. Temperature dependence of the real part of the susceptibility for various a.c. magnetic fields. HLC. is the amplitude of measuring field applied perpendicular to the crystal b-axis.
x’/Ib
HAC
axis
• 0.017 Oe 0 0.034 Oe a 0.34 Oe 0 0.68 Oe fa7OHz Hoc:O
a6
00’O~
0S 0,. 0
• 0~
a
S
a
0 0
0•
a
0
a
a0
. 0
a
0
0
•.
0a
50
100
150
•
0
a~
A° 200
A
oOo.a.A0
250
I (mK)
Fig. 2. Temperature dependence of the real part of the susceptibility for various a.c. magnetic fields. ~ to the crystal b-axis. orientation as a standard for calibration. The Sn—Pb alloy transformed to the superconducting state at 7.5 K. Below the transition temperature the alloy is in the perfect diamagnetic state and xo is l/4ir. In the normal state the a.c. field penetrates the alloy sufficiently as the skin depth is large enough compared to the size of the specimen. Since the demagnetizing effect is taken to be similar to either the alloy or (SN)~,we can obtain the true susceptibility of (SN)~with the standard procedure by correcting the volume difference between the two. —
is parallel
We observed no frequency dependence. This means that the eddy current heating by a.c. magnetic field was negligible. The shielding effect in the normal state could also be neglected. Moreover, no hysteresis in the susceptibility was observed with either field or temperature sweeps. For three sets of specimens mentioned above we obtained nearly identical results in magnitude and the behavior of susceptibility. This may be an indication that the crystals prepared were uniform in quality. In this paper signs of II and .1. indicate the parallel
THE MEISSNER EFFECT OF POLYSULFUR NITRIDE, (SN)~
Vol. 32, No. 8
661
xjb axis (normaLized) 1.(
D
aD a
N
a
a
D
D
34mK
a
63mK l9lmK
0
f:7OHz HDCOO
a 0
C
a
D
—
—I
~0.5
a 0 A 0
D
a 0 0 0 00 0
0
0.2
0
0:6 HAC(Oe)
Fig. 3.H dependence of the susceptibifity for various temperatures. All the data are normalized at ~ is perpen’dicular to the b-axis.
=
~.
I
I
X~jb axis
g
a
a
I
0. HLC
I
(normalized) a
a
34mK 63mK ol9lmK a
~
0 0
70 Hz HACaO.034 Oe 0 0 0 0
I
0
0.5
1.0
I
I
I
1.5
2.0
2.5
3.0
HDC (Oe)
Fig. 4. HdC dependence of the susceptibility for various temperatures. HLC is fixed at 0.034 Oe HLc and HdC are -
applied in the same direction perpendicular to the b-axis. The data are normalized at HdC. and the perpendicular direction to the b-axis respectively. The measurements throughout the plane normal to the b-axis are not specially distinguished since (SN)~ is isotropic magnetically as reported by Azevedo eta!. [3] This was also re-examined in our experiment, The temperature dependence of x~at Hd.c = 0 is shown in Fig. 1. With decrease of temperature for HLC <0.0340e, x~ increases rapidly at first and then the change becomes quite gradual and nearly saturates .
=
0.
at about 100 mK. From the comparison with the change of susceptibility of the Sn—Pb alloy, we have obtained for (SN)~a susceptibility (xe)) of 93 ±7% of 1 /4ir at 30 mK. It is concluded that (SN)~is essentially in the perfect diamagnetic state in this temperature region when the weak field is applied perpendicular to the b-axis. For each magnitude of a.c. magnetic field, it is possible to find a temperature T~,at which the —
THE MEISSNER EFFECT OF POLYSULFUR NITRIDE, (SN)~
662
X’l b f7OHz
Vol. 32, No. 8
axis
HDCOO
HACOO,680e
5 C
0
>.
0
0
23 00
a
L
0
0
00
0
.0 0 0
0
50
100 I
150 (mK)
200
0p
•.g~
250
Fig. 5. A typical example of the temperature dependence of the imaginary part of the susceptibility. HLC. is applied perpendicular to the b-axis with amplitude of 0.68 Oe at 70Hz. susceptibility curve begins to rise from the horizontal axis. We define T~as a superconducting transition temperature. For (SN)~,both T~and x~depend markedly on Hac. When the field is higher than 0.34 Oe we can expect no more saturation for x~ even below 5OmK. With increase of magnetic field, T~shifts towards lower temperatures and the rise of x~with the reducing temperature becomes more gradual. The temperature dependence of X~iat HdC = 0 is shown in Fig. 2. With decrease of temperature for ~ <0.0340e, x~tends to the saturation below 50mK. From the calibration with the standard specimen of Sn—Pb alloy, it is deduced that the susceptibility (Xo) at 30 mK is 65 ±10% of l/4ir. This means that some fractionsof the magnetic flux penetrate into the crystal even at low enough temperatures when the field is parallel to the b-axis, As is seen in Fig. 2, the rise of x~with temperature is more gradual than x~shown in Fig. 1. Though the determination of T 4~from X~Iincludes some ambiguity, it could be concluded that T0 from ~ coincides with that from x’~at the same magnitude ofHac. In the limit HLC 0 at Hd~= 0, T~= 250 ±3 mK for both Xi and X~i~ Figures 3 and 4 show the dependence of xi on H,,.~ and Hdc respectively. xi at 191 mK depends notably Ofl Hac and HdC. The feature is particular for HLC. Such a tendency is seen to occur at a region where the magnitude of xi changes sensitively with temperature The dependence of xi on HLC, becomes less marked and that on HdC is negligible at temperatures where the susceptibility nearly saturates. The changes of x~with HLC and HdC are similar to x —
-~
-
~.
The imaginary part of the susceptibility (x”) is related with the energy loss of the a.c. field. In the normal state, the resistivity of (SN)~is not so small and the loss by the eddy current can be neglected. In the transition region, the loss will increase due to the reduction of the electrical resistance. With further lowering of temperature the loss decreases again due to the increase of Meissner region. At the perfect diamagnetic state the loss vanishes. As a whole there appears a peak in x” as temperature sweeps. An example of x~at Hac = 0.68 Oe is shown in Fig. 5. The peak of x” at about 100 mK will correspond to the maximum loss. At the peak it is found that ix~Ix~ = 0.47. It is found that x” depends markedly on Hac. With the decrease of Hac, x” decreases rapidly and the peak shifts towards the higher temperature region. For example, at Hac = 0.017 Oe, the peak of~~ moves to about 200 mK where I x~Ix~ = 0.04. This means that the loss due to the a.c. magnetic field increases rapidly with increase 0fHLC, and the occurrence of the Meissner effect is strongly suppressed. In conclusion, we have found the almost perfect diamagnetism of (SN)~for weak field in the perpendicular direction to the molecular chain and not perfect diamagnetism in the parallel direction. The range of transition temperature is very wide. Similar temperature dependence has been observed in superconductivity of fine particles whose dimensions are less than the coherence length [13], though the absolute value of the susceptibility does not coincide quantitatively. A remarkable dependence of the susceptibility of (SN)~ on Hac has never been observed in ordinary superconductors. These phenomena seem to be explained by considering the one dimensional structure of (SN)~.
Vol. 32, No.8
THE MEISSNER EFFECT OF POLYSULFUR NITRIDE, (SN)~
The details of the study, as well as those of x” and other electrical properties, wifi be reported in the near future. Acknowledgement The authors thank Dr. S. Tamura for his helpful instruction in the measurement of the specific gravity of (SN)~. —
REFERENCES 1.
R.L. Greene, G.B. Street & L.J. Suter,Phys. Rev. Lett. 34, 577 (1975). 2. R.L. Greene & G.B. Street,1~oc.ofNA TO-ASI on Chemist,y and Physics ofOne-Dimensional Metals, (Edited by H.J. Keller), r~.167. Plenum Press, New York (1977). 3. L.J. Azevedo, W.G. Clark, G. Deutscher, R.L. Greene, G.B. Street & L.J. Suter, Solid State Commun. 19, 197 (1976). 4. R.L. Civiak, C. Elbaum, W. Junker, C. Gouch, H.!. Kao, LF. Nicholas & M.M. Labes, Solid State Commun. 18. 1205 (1976~.
663
R.L. Civiak, C. Elbaum, L.F. Nicholas, H.I. Kao & M.M. Labes, Phys. Rev. B14, 5413 (1976). 6. R.H. Dee, A.J. Berlinsky, J.F. Carolan, E. Klein, N.J. Stone,22, B.G. & G.B. Street, Solid State Commun. 303Turrell (1977). 7. R.H. Dee, D.H. Dollard, B.G. Turrell & J.F. Carolan, Solid State Commun. 24,469 (1977). 8. C.M. Mikuiski, PJ. Russo, M.S. Saran, A.G. MacDiarmid, A.F. Garito & A.J. Heeger, J. Amer. Chem. Soc. 97, 6358 (1975). 9. J.F. Schooley, R.J. Soulen, Jr. & G.A. Evans, Jr., 5.
10. 11. 12.
13.
NBS Special Publication 260-44(1972).
Y. Oda, G. Fujii & H. Nagano, Ciyogenics 14, 84 (1974). Y. Oda, G. Fujii & H. Nagano, Cryogenics 18, 73 (1978). W.R. Abel, A.C. Anderson & J.C. Wheatley, Rev. Sci. Instrum. 35, 444(1964). T. Takahara, S. Kobayashi& W. Sasaki,J. Phys. Soc. Japan 32, 1668 (1972).