- Email: [email protected]
dHvA measurements of high-Tc oxides with steady high-magnetic fields
J. Phys. Chrm. Solid.~ Vol. Printed in Great Britain.
53. No.
12. pp. 155%IXQ.
0022~3697/W $5.00 + 0.00 0 1992PUgWl3llPWLtd
1992
dHvA MEASUREMENTS
OF HIGH-Tc OXIDES WITH
STEADY HIGH-MAGNETIC
FIELDS
G. KIDG’, H. KATAYAMA-YOSHIDA’, and T. TAKAHASH12 ‘Institute for Materials Research, Tohoku University,
Sendai 980, Japan
‘Department of Physics, Tohoku University, Sendai 980, Japan
ABSTRACT - The de Haas-van Alphen (dHvA) effect has been measured in YBasCus0, (Y 123) and Tl,Ba&!uO~s (T12201) with oriented-powder samples in H//c-axis direction at the temperature range between 1.6 and 4.2 K with steady high magnetic fields up to 27 T. The oscillatory magnetization was detected by a modulation technique. We performed spectral analysis by employing the maximum entropy method (MEM). In Y123, the spectral density shows a peak at 456T which corresponds to an extremal cross-section of 0.044 A2. The dingle temperature was evaluated to be 7 K using the effective-mass-value of 2.14,. In T12201, the maximum of spectral density appeared at 400 T not only for superconducting sample (6 = .08) but also for metallic non-superconducting sample (6 = .l).
Keywords:
oxide superconductor, de Haas van Alphen, Fermi surface, Hybrid magnet
INTRODUCTION Since the oxide superconductors were discovered, much attention has been paied to figure out the nature of the strange normal state properties. The presence of large Fermi surface has been suggested by the experimental results such as angle-resolved photoemission, two-dimensional angular correlation of positron annihilation radiation, etc. (see, Takahashi et al. 1988, and Smedskjaer et al. 1988) The measurement of de Haas-van Alphen (dHvA) effect is a direct way to investigate Fermi surface in materials. Los Alamos group first reported the oscillation in Y123 powder sample at the field range up to 100 T using microsecond pulsed magnetic fields generated by an explosive driven flux compression method (see, Muellar at al. 1991). Their latest oscillatory frequencies reported are 530 and 780 T (see, Fowler et al. 1992). More precise measurements are expected using steady high magnetic fields, if the condition o,z>l is satisfied. We measured dHvA effect with a hybrid magnet using a modulation technique, and found a broad band in FFT spectrum for Y123 powder around 500 T (see, Kido et al. 1990 and 1991). Generally, the FFI spectral analysis requires several tens of oscillations, while the oscillatory amplitude increases steeply depending on the magnetic field intensity. In such a case, a spectral analysis based on the data in only high magnetic field is appropriate to determine the oscillatory frequency. We have carried out the waveform analysis by means of the maximum entropy method (MEM), and found a distinguished spectral density peak at 456f35 T. We have also measured dHvA effect in Tl,Ba$uO,, (T12201) system, and determined the extremal cross-section area. In T12201 system, the critical temperature of superconducting transition can be controlled by the excess oxygen fraction from 6 without changing the crystal structure (see, Kubo et al. 1991). A metallic sample (8 =
0.1) of non-superconductor and a high temperature superconductor with Tc = 20 K (8 = 0.08) were prepared for the measurement. This system proved to be suitable materials to investigate the Fermi surface of superconducting oxide.
EXPERIMENTAL The YBa2Cu3C+ samples were prepared by conventional sintering technique at Osaka University. The powder was ground into fine crystallites with diameters smaller than 20 pm. The c-axes of the crystallites were aligned by a 5 T field during the hardening process of a mixture of the crystallites and epoxy resin. We prepared several samples, #l through #4, with different sintering process. 1555
1556
G. Km0 et al.
Tl,Ba$uO,, powder was prepared by a high-T&group of NEC Corporation. At first, metallic samples were fabricated by sintering raw materials in oxygen atmosphere, which is denoted as nonsuperTl2201. The superconducting samples were made by annealing the metallic sample in argon at the proper temperature for 3-5 hours. The transition temperature of the sample is precisely controlled by the annealing temperature. A superconducting Tl,Ba$uO,, with Tc=2O K was used in the present experiments which will be indicated as super-T12201. The oxygen fraction 6 is estimated to be approximately 0.08. Each sample was ground into fine crystallites of about 30 pm and was mixed into the epoxy resin. A 14 T field was used in the hardening process for T12201 system. The inclination from the c-axis was less than 3 degrees, which was confirmed by the NMR method. Steady high magnetic fields were generated by hybrid magnets, HMl and HM2, installed at Institute for Materials Research, Tohoku University. The magnets HMl and HM2 can generate 28 T and 23 T for 52 mm bore, respectively. The oscillatory part of the magnetization corresponding to the de Haas-van Alphen effect was extracted by a modulation technique. The amplitude and the frequency of the modulation are approximately 10 mTpp and 1.35 kHz, respectively. By using four balanced Since the modulation is small, we use pickup-coils four samples can be measured simultaneously. l-f signal as the reference of the lock-in amplifiers. The samples were soaked in liquid helium directly, and the temperature was changed from 1.6 to 4.3 K by controlling vapor pressure of He. The details of the apparatus was reported previously (see, Kido et al. 199 1).
RESULTS
AND
DISCUSSION
(1) YBQ u,O, Figure 1 shows the best FVT spectra of the YBa.$u,O, samples at different temperatures. A broad band appears around SOOTin the AC susceptibility even at 3.1 K. We have evaluated the effective mass to be 2. lfOSm, by analyzing the dependence of spectral amplitude on the temperature (see, Kido et al. 1991). Here m, is the mass of a free electron.
YBaKu307-6 H /I c-axis
Frequency
Fig. 1:
[ kT I
Spectral density of ITT analysis in YBa,Cu,Q at 1.8 and 3.1 K.
In the FFT analysis, the most smooth curve was obtained when using the data between 10 and 23T. Namely, approximately 30 periods of the dHvA oscillation are included in this field range. In general, FFT spectral analysis requires several tens of oscillations, though the dHvA oscillatory amplitude strongly depends on the magnetic field intensity. A spectral analysis based on the data in the narrow
dHvA measurements of high-T, oxides
1557
magnetic field range is appropriate to determine the oscillatory frequency. Figure 2 shows MEM spectral density curves transformed from the data in the range of 18 to 21T and that from 22 to 27 T, respectively, A sharp peak appears around 46OTin both cases. Since the experiments were carried out in superconducting state, spurious signal due to the movement of pinned flux is much larger than signal from dHvA effect. Therefore, the observed oscillation frequency scatters somewhat.
YBazCus07 Smple
Fig. 2:
Table 1:
m
Spectral density of MEM analysis in YBa&h&
at different field ranges.
Oscillation frequencies of YEIazcUsO, observed at various conditions.
MngttrllGDnle
I~Plige[q
llM90JL24F3
18.0, 22.8
PII-
I.0
420
II
18.6, 22.3
420
x2
1.8
F3
18.0, 22.3
440
13
I.8
-Il_-
--
I.8
15.8, 22R *
460
II
2.5
Dt
160, 22.8
420
I2
2.6
D3
f8.0, 22.8
130
--b_ 13
24.3, 26.6
420
12 ---we....
. P-e--
I%4
--
.--
24.0, 26.7
510
22.2, 26.8 d56 . ..__ _......” . .
(4
.
2.5 ._l_.-.__. l.8 _.-
1.8
x2 IA .__-_,_____ .__.._
Dd
22.2, 26.8 _.____._-
-_-_ 420
t4
I.8
E2
183,21.2
470
a2
I____-
1.8
520
--.
154
ilM9iJUl2CI c2 Avcmgc
I3
dR@
19.2, 22.1
flM90JLl2D2
w-.
Temp. (K)
lil
llM90,tL13121 ,_-_I
SimpIe
F2
IIMDOJL2dI~l -...-
Ftcq (x)
18.0, 21.2
--
14
-_
I.8
22.0, 22.8
500
XI
1.6
20.0, 22.8
486
I2
I.6
456(S)
1558
G. Km0 er al.
Experimental results of 4 different samples at various conditions are listed in Table 1, in which the average frequency was determined to be 456535 T . This value corresponds to the extremal cross section of 0.044fo.003 A”, which agrees quite well with the theoretical value (0.042 A”) of the columnar Fermi surface around the S-point containing CuO chain and CuO, layer characters (see, Massidda et al. 1987 and Pickett et al. 1992). By the use of MEM, the spectral analysis of the magnetic filed dependence on the spectral intensity becomes clearer, because only a few oscillation is enough to determine the oscillatory frequency. However, it should be noted that in the MEM analysis, the spectral intensity depends on not only the dHvA oscillation amplitude but also on the spurious signal amplitude. So that, it may not be effective to apply MEM for the analysis of temperature dependence of amplitude especially in the superconducting state, because a background noise differs according to the states of materials. The field dependence of the oscillatory amplitude by the MEM analysis give satisfied results when the conditions are assured. In the present experimental condition, the amplitude of AC susceptibility due to the de Haas-van Alphen effect is expressed as: A = aTB’* x exp ( -21t’ k,m*(T+TJe
h B),
(1)
where T,, is Dingle temperature, m* the effective mass of carrier, k, Boltzmann constant, 01proportional constant, respectively. The Dingle temperature can be derived reversely from the slope of log(A B*F> vs. l/B plot at the fixed temperature (see Fig. 3). The Dingle temperature was evaluated to be 7 K using m*=2.lm, which seems somewhat higher than 1.7 K reported by the Los Alamos group (see, Fowler et al. 1992). This is due to the difference in effective mass used in the calculation.
I’ ’ ’ ’ ’ ’ ’ ’ ’ ’ ’ ’ ’ ’ ‘1 II-
P6 2 g
J-
2-
Fig. 3: log(ABsR17?vs. l/Bplot at 1.8 K.
(2) T12B@u0,+o The AC magnetic susceptibility versus magnetic field of superconducting and metallic samples is shown An oscillation can be seen above 20 T for the super-T12201. The MEM analysis was in Fig. 4. made based on the data between 20 and 23 T. The solid line indicates the MEM spectrum for the superconducting sample exhibiting spectral density peak at 400 T.
dHvA measurementsof high-T’ oxides
1559
Fig. 4: AC magnetic susceptibility in super and metallic TlBa,CuO,.
As for non-superconducting sample, in spite of the large back ground signal, a small peak happened to appear at the same frequency. This may suggest that the Fermi surface corresponding to this frequency does not change so much by the oxygen traction. In the Energy-band diagram of T12201, calculatedby Hamann and Mattheis, a small electron ellipsoid is realized at the gamma point (see, Hamann er al. 1988). What we observed may correspond to this surface.
Tl2Ba2CuOw BllC-UrS 1.6 K 20-23 T
:: Non-soper : Y \
Fig. 5: Spectraldensity of MEM analysis in TlBa&hO~
1560
G. Kmo et al.
Our experiments were carried out in the mixed state in Y 123, which was confhmed by the magnetization measurement up to 30T. Observation of the dHvA oscillation in the mixed state was first reported in NbSe, by (Graebner et al. 1988), and was precisely investigated by (Gnuki et al. 1992). The possibility to observe the dHvA effect in the mixed state was first argued theoretically by (Markiewcz et al. 1988) and several works successively appeared (see, Miyake) which attracted much attention of scientist in this field.
CONCLUSIONS
The dHvA effect in Y123 and T12201 was investigated in steady high magnetic field up to 27 T. In Y123, the dHvA frequency originating from the cylinder at the S point of Broullian zone was determined to be 456 T. In T12201, a peak originating from ellipsoid at the r point was observed at 400 T.
ACKNOWLEDGMENTS
We wish to thank Professor. Y. Kitaoka and his group for giving us their best quality Y123 samples. Thanks are also due to Dr. Y. Kubo, Y. Shimakawa , T. Manako, and H. Igarashi for providing us T1220 1 samples. This work is partly supported by the Grant-in-aid for Scientific Research on priority Areas from the Ministry of Education, Science, and Culture.
REFERENCES: T. Takahasi, H. Matsuyama, H. Katayama-Yoshida, Y. Okabe. S. Hosoya, K. Seki, H. Fujimoto, Recent works on photoemission and positron and H. Inokuchi, Nature 334 (1988) 691., annihilation are summarized in Proc. Workshopon Fermiogy of High-Tc Superconductors : J. Phys. Chem. Solids 5 2 (1991) 1401. L. C. Smedskjaer, J. Z. Liu, R. Benedek, DGLegnini, D.J. Lam, M.D. Stahulak, H. Claus, and A. P. Y. Bansil, Physica 156 C (1988) 269. F.M. Mueller, C.M. Fowler, B.L. Freeman, W.L. Hults, J.C. King, and J.L. Smith, Physica B 17 2 (1991) 253. C.M. Fowler, B.L. Freeman, W.L. Hults, J.C. King, F.M. Mueller, and J.L. Smith, Phys. Rev. Lett. 6 8 (1992) 534. G. Kido, K. Komorita, H. Katayama-Yoshida, T. Takahashi, Y. Kitaoka, K. Ishida, and T. Yoshitomi, Proc. 3rd Int. Symp. on Superconductivity, (Sendai, 1990) Springer-Verlag pp. 237: G. Kido, H. Katayama-Yoshida, T. Takahashi J. Phys. Chem. Solids 5 2 (1991) 1465. Y. Kubc, Y. Shimakawa, T. manako, and H. Igarashi, Phys Rev. B 43 (1991) 7875. S. Massidda, J. J. Yu, A. J. Freeman, and D. D. Koelling, Phys. Lett. 122A (1987) 198. W.E. Pickett, H. Krakauer, R.E. Cohen, and D.J. Singh, Science 2 5 5 (1992) 46. D. R. Hamann, and L. F. Mattheiss, Phys. Rev. B 3 8 (1988) 5138. J. E. Graebner, and M. Robbins, Phys. Rev. Lett. 2 3 (1976) 422. Y. Onuki, I. Umehara, T. Ebihara, N. Nagai, and K. Tanaka, J. Phys. Sot. Jpn. 6 1 (1992) 692. R.S. Markiewicz, L.D. Vagner, P. Wyder, and T. Maniv, Solid State Commu. 6 7 (1988) 43. K. Miyake, Proc. Int. Conf, on StronglyCorrelated Electron Systems: to appear in Physica B (1993).
53. No.
12. pp. 155%IXQ.
0022~3697/W $5.00 + 0.00 0 1992PUgWl3llPWLtd
1992
dHvA MEASUREMENTS
OF HIGH-Tc OXIDES WITH
STEADY HIGH-MAGNETIC
FIELDS
G. KIDG’, H. KATAYAMA-YOSHIDA’, and T. TAKAHASH12 ‘Institute for Materials Research, Tohoku University,
Sendai 980, Japan
‘Department of Physics, Tohoku University, Sendai 980, Japan
ABSTRACT - The de Haas-van Alphen (dHvA) effect has been measured in YBasCus0, (Y 123) and Tl,Ba&!uO~s (T12201) with oriented-powder samples in H//c-axis direction at the temperature range between 1.6 and 4.2 K with steady high magnetic fields up to 27 T. The oscillatory magnetization was detected by a modulation technique. We performed spectral analysis by employing the maximum entropy method (MEM). In Y123, the spectral density shows a peak at 456T which corresponds to an extremal cross-section of 0.044 A2. The dingle temperature was evaluated to be 7 K using the effective-mass-value of 2.14,. In T12201, the maximum of spectral density appeared at 400 T not only for superconducting sample (6 = .08) but also for metallic non-superconducting sample (6 = .l).
Keywords:
oxide superconductor, de Haas van Alphen, Fermi surface, Hybrid magnet
INTRODUCTION Since the oxide superconductors were discovered, much attention has been paied to figure out the nature of the strange normal state properties. The presence of large Fermi surface has been suggested by the experimental results such as angle-resolved photoemission, two-dimensional angular correlation of positron annihilation radiation, etc. (see, Takahashi et al. 1988, and Smedskjaer et al. 1988) The measurement of de Haas-van Alphen (dHvA) effect is a direct way to investigate Fermi surface in materials. Los Alamos group first reported the oscillation in Y123 powder sample at the field range up to 100 T using microsecond pulsed magnetic fields generated by an explosive driven flux compression method (see, Muellar at al. 1991). Their latest oscillatory frequencies reported are 530 and 780 T (see, Fowler et al. 1992). More precise measurements are expected using steady high magnetic fields, if the condition o,z>l is satisfied. We measured dHvA effect with a hybrid magnet using a modulation technique, and found a broad band in FFT spectrum for Y123 powder around 500 T (see, Kido et al. 1990 and 1991). Generally, the FFI spectral analysis requires several tens of oscillations, while the oscillatory amplitude increases steeply depending on the magnetic field intensity. In such a case, a spectral analysis based on the data in only high magnetic field is appropriate to determine the oscillatory frequency. We have carried out the waveform analysis by means of the maximum entropy method (MEM), and found a distinguished spectral density peak at 456f35 T. We have also measured dHvA effect in Tl,Ba$uO,, (T12201) system, and determined the extremal cross-section area. In T12201 system, the critical temperature of superconducting transition can be controlled by the excess oxygen fraction from 6 without changing the crystal structure (see, Kubo et al. 1991). A metallic sample (8 =
0.1) of non-superconductor and a high temperature superconductor with Tc = 20 K (8 = 0.08) were prepared for the measurement. This system proved to be suitable materials to investigate the Fermi surface of superconducting oxide.
EXPERIMENTAL The YBa2Cu3C+ samples were prepared by conventional sintering technique at Osaka University. The powder was ground into fine crystallites with diameters smaller than 20 pm. The c-axes of the crystallites were aligned by a 5 T field during the hardening process of a mixture of the crystallites and epoxy resin. We prepared several samples, #l through #4, with different sintering process. 1555
1556
G. Km0 et al.
Tl,Ba$uO,, powder was prepared by a high-T&group of NEC Corporation. At first, metallic samples were fabricated by sintering raw materials in oxygen atmosphere, which is denoted as nonsuperTl2201. The superconducting samples were made by annealing the metallic sample in argon at the proper temperature for 3-5 hours. The transition temperature of the sample is precisely controlled by the annealing temperature. A superconducting Tl,Ba$uO,, with Tc=2O K was used in the present experiments which will be indicated as super-T12201. The oxygen fraction 6 is estimated to be approximately 0.08. Each sample was ground into fine crystallites of about 30 pm and was mixed into the epoxy resin. A 14 T field was used in the hardening process for T12201 system. The inclination from the c-axis was less than 3 degrees, which was confirmed by the NMR method. Steady high magnetic fields were generated by hybrid magnets, HMl and HM2, installed at Institute for Materials Research, Tohoku University. The magnets HMl and HM2 can generate 28 T and 23 T for 52 mm bore, respectively. The oscillatory part of the magnetization corresponding to the de Haas-van Alphen effect was extracted by a modulation technique. The amplitude and the frequency of the modulation are approximately 10 mTpp and 1.35 kHz, respectively. By using four balanced Since the modulation is small, we use pickup-coils four samples can be measured simultaneously. l-f signal as the reference of the lock-in amplifiers. The samples were soaked in liquid helium directly, and the temperature was changed from 1.6 to 4.3 K by controlling vapor pressure of He. The details of the apparatus was reported previously (see, Kido et al. 199 1).
RESULTS
AND
DISCUSSION
(1) YBQ u,O, Figure 1 shows the best FVT spectra of the YBa.$u,O, samples at different temperatures. A broad band appears around SOOTin the AC susceptibility even at 3.1 K. We have evaluated the effective mass to be 2. lfOSm, by analyzing the dependence of spectral amplitude on the temperature (see, Kido et al. 1991). Here m, is the mass of a free electron.
YBaKu307-6 H /I c-axis
Frequency
Fig. 1:
[ kT I
Spectral density of ITT analysis in YBa,Cu,Q at 1.8 and 3.1 K.
In the FFT analysis, the most smooth curve was obtained when using the data between 10 and 23T. Namely, approximately 30 periods of the dHvA oscillation are included in this field range. In general, FFT spectral analysis requires several tens of oscillations, though the dHvA oscillatory amplitude strongly depends on the magnetic field intensity. A spectral analysis based on the data in the narrow
dHvA measurements of high-T, oxides
1557
magnetic field range is appropriate to determine the oscillatory frequency. Figure 2 shows MEM spectral density curves transformed from the data in the range of 18 to 21T and that from 22 to 27 T, respectively, A sharp peak appears around 46OTin both cases. Since the experiments were carried out in superconducting state, spurious signal due to the movement of pinned flux is much larger than signal from dHvA effect. Therefore, the observed oscillation frequency scatters somewhat.
YBazCus07 Smple
Fig. 2:
Table 1:
m
Spectral density of MEM analysis in YBa&h&
at different field ranges.
Oscillation frequencies of YEIazcUsO, observed at various conditions.
MngttrllGDnle
I~Plige[q
llM90JL24F3
18.0, 22.8
PII-
I.0
420
II
18.6, 22.3
420
x2
1.8
F3
18.0, 22.3
440
13
I.8
-Il_-
--
I.8
15.8, 22R *
460
II
2.5
Dt
160, 22.8
420
I2
2.6
D3
f8.0, 22.8
130
--b_ 13
24.3, 26.6
420
12 ---we....
. P-e--
I%4
--
.--
24.0, 26.7
510
22.2, 26.8 d56 . ..__ _......” . .
(4
.
2.5 ._l_.-.__. l.8 _.-
1.8
x2 IA .__-_,_____ .__.._
Dd
22.2, 26.8 _.____._-
-_-_ 420
t4
I.8
E2
183,21.2
470
a2
I____-
1.8
520
--.
154
ilM9iJUl2CI c2 Avcmgc
I3
dR@
19.2, 22.1
flM90JLl2D2
w-.
Temp. (K)
lil
llM90,tL13121 ,_-_I
SimpIe
F2
IIMDOJL2dI~l -...-
Ftcq (x)
18.0, 21.2
--
14
-_
I.8
22.0, 22.8
500
XI
1.6
20.0, 22.8
486
I2
I.6
456(S)
1558
G. Km0 er al.
Experimental results of 4 different samples at various conditions are listed in Table 1, in which the average frequency was determined to be 456535 T . This value corresponds to the extremal cross section of 0.044fo.003 A”, which agrees quite well with the theoretical value (0.042 A”) of the columnar Fermi surface around the S-point containing CuO chain and CuO, layer characters (see, Massidda et al. 1987 and Pickett et al. 1992). By the use of MEM, the spectral analysis of the magnetic filed dependence on the spectral intensity becomes clearer, because only a few oscillation is enough to determine the oscillatory frequency. However, it should be noted that in the MEM analysis, the spectral intensity depends on not only the dHvA oscillation amplitude but also on the spurious signal amplitude. So that, it may not be effective to apply MEM for the analysis of temperature dependence of amplitude especially in the superconducting state, because a background noise differs according to the states of materials. The field dependence of the oscillatory amplitude by the MEM analysis give satisfied results when the conditions are assured. In the present experimental condition, the amplitude of AC susceptibility due to the de Haas-van Alphen effect is expressed as: A = aTB’* x exp ( -21t’ k,m*(T+TJe
h B),
(1)
where T,, is Dingle temperature, m* the effective mass of carrier, k, Boltzmann constant, 01proportional constant, respectively. The Dingle temperature can be derived reversely from the slope of log(A B*F> vs. l/B plot at the fixed temperature (see Fig. 3). The Dingle temperature was evaluated to be 7 K using m*=2.lm, which seems somewhat higher than 1.7 K reported by the Los Alamos group (see, Fowler et al. 1992). This is due to the difference in effective mass used in the calculation.
I’ ’ ’ ’ ’ ’ ’ ’ ’ ’ ’ ’ ’ ’ ‘1 II-
P6 2 g
J-
2-
Fig. 3: log(ABsR17?vs. l/Bplot at 1.8 K.
(2) T12B@u0,+o The AC magnetic susceptibility versus magnetic field of superconducting and metallic samples is shown An oscillation can be seen above 20 T for the super-T12201. The MEM analysis was in Fig. 4. made based on the data between 20 and 23 T. The solid line indicates the MEM spectrum for the superconducting sample exhibiting spectral density peak at 400 T.
dHvA measurementsof high-T’ oxides
1559
Fig. 4: AC magnetic susceptibility in super and metallic TlBa,CuO,.
As for non-superconducting sample, in spite of the large back ground signal, a small peak happened to appear at the same frequency. This may suggest that the Fermi surface corresponding to this frequency does not change so much by the oxygen traction. In the Energy-band diagram of T12201, calculatedby Hamann and Mattheis, a small electron ellipsoid is realized at the gamma point (see, Hamann er al. 1988). What we observed may correspond to this surface.
Tl2Ba2CuOw BllC-UrS 1.6 K 20-23 T
:: Non-soper : Y \
Fig. 5: Spectraldensity of MEM analysis in TlBa&hO~
1560
G. Kmo et al.
Our experiments were carried out in the mixed state in Y 123, which was confhmed by the magnetization measurement up to 30T. Observation of the dHvA oscillation in the mixed state was first reported in NbSe, by (Graebner et al. 1988), and was precisely investigated by (Gnuki et al. 1992). The possibility to observe the dHvA effect in the mixed state was first argued theoretically by (Markiewcz et al. 1988) and several works successively appeared (see, Miyake) which attracted much attention of scientist in this field.
CONCLUSIONS
The dHvA effect in Y123 and T12201 was investigated in steady high magnetic field up to 27 T. In Y123, the dHvA frequency originating from the cylinder at the S point of Broullian zone was determined to be 456 T. In T12201, a peak originating from ellipsoid at the r point was observed at 400 T.
ACKNOWLEDGMENTS
We wish to thank Professor. Y. Kitaoka and his group for giving us their best quality Y123 samples. Thanks are also due to Dr. Y. Kubo, Y. Shimakawa , T. Manako, and H. Igarashi for providing us T1220 1 samples. This work is partly supported by the Grant-in-aid for Scientific Research on priority Areas from the Ministry of Education, Science, and Culture.
REFERENCES: T. Takahasi, H. Matsuyama, H. Katayama-Yoshida, Y. Okabe. S. Hosoya, K. Seki, H. Fujimoto, Recent works on photoemission and positron and H. Inokuchi, Nature 334 (1988) 691., annihilation are summarized in Proc. Workshopon Fermiogy of High-Tc Superconductors : J. Phys. Chem. Solids 5 2 (1991) 1401. L. C. Smedskjaer, J. Z. Liu, R. Benedek, DGLegnini, D.J. Lam, M.D. Stahulak, H. Claus, and A. P. Y. Bansil, Physica 156 C (1988) 269. F.M. Mueller, C.M. Fowler, B.L. Freeman, W.L. Hults, J.C. King, and J.L. Smith, Physica B 17 2 (1991) 253. C.M. Fowler, B.L. Freeman, W.L. Hults, J.C. King, F.M. Mueller, and J.L. Smith, Phys. Rev. Lett. 6 8 (1992) 534. G. Kido, K. Komorita, H. Katayama-Yoshida, T. Takahashi, Y. Kitaoka, K. Ishida, and T. Yoshitomi, Proc. 3rd Int. Symp. on Superconductivity, (Sendai, 1990) Springer-Verlag pp. 237: G. Kido, H. Katayama-Yoshida, T. Takahashi J. Phys. Chem. Solids 5 2 (1991) 1465. Y. Kubc, Y. Shimakawa, T. manako, and H. Igarashi, Phys Rev. B 43 (1991) 7875. S. Massidda, J. J. Yu, A. J. Freeman, and D. D. Koelling, Phys. Lett. 122A (1987) 198. W.E. Pickett, H. Krakauer, R.E. Cohen, and D.J. Singh, Science 2 5 5 (1992) 46. D. R. Hamann, and L. F. Mattheiss, Phys. Rev. B 3 8 (1988) 5138. J. E. Graebner, and M. Robbins, Phys. Rev. Lett. 2 3 (1976) 422. Y. Onuki, I. Umehara, T. Ebihara, N. Nagai, and K. Tanaka, J. Phys. Sot. Jpn. 6 1 (1992) 692. R.S. Markiewicz, L.D. Vagner, P. Wyder, and T. Maniv, Solid State Commu. 6 7 (1988) 43. K. Miyake, Proc. Int. Conf, on StronglyCorrelated Electron Systems: to appear in Physica B (1993).