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Increase of pinning by hydrogenation in 1-2-3 and 2-1-4 types superconductors
PHISlCA
Physica C 235-240 (1994)3041-3042 North-Holland
Increase o f pinning by hydrogenation in 1-2-3 and 2-1-4 types superconductors J.Klamut, M.Ciszek, H.Drulis, P.W.Klamut, K.Nied2wied2, B.Nowak, J.Olejniczak, A.J.Zaleski, O.J.Zogal, Institute of Low Temperatures and Structure Research, PAS. P.O.Box 937, 50-950 Wroclaw, Poland and International Laboratory, of High Magnetic Fields and Low Temperatures, Wroclaw, Poland Ac losses in ceramic Y-Ba-Cu-O and NMR and Mfssbauer studies of ceramic La-Sr-Cu-O superconductors before and after hydrogenation are presented. Two-phase behaviour of hydogenated samples, increased pinning and increased intragranular critical current density is evidenced. 1. Introduction
Almost immediately after the discovery of the high temperature superconductivity, works begun on the influence of hydrogenation on physical properties of this new class of superconductors. The first publications in this field appeared just in 1987 [1]. There is general agreement that introduction of hydrogen may reduce the number of holes (charge carriers in p-type high-T c ceramics) and that the material may become semiconducting and magnetic at high hydrogen concentrations. In 1-2-3 ~,pe superconductors the diminishing of ox.ygen content and increase of hydrogen content can act in similar way [2]. By hydrogenation non-superconducting regions may be created. These non superconducting inclusions can play the role of the pinning centers [3]. The above interpretation is in agreement xx~ith the results of investigation of the influence of hydrogen doping in YBa2Cu30 v on intragranular and intergranular critical currentg [4]. 2. Results and discussion
It is shown that introduction of hydrogen decreases the critical current between the grains simultaneously increasing the critical current inside the grains. On this basis a supposition was formulated stating that hydrogen weakens the Josephson links responsive for the intergranular currents while increasing pinning inside the grains, responsible for the intraganular critical current. The dependence of the lossy component g" of magnetic permeability for YBa2Cu30 7 on the external field anaplitude bo for non-hydrogenated and hydrogenated samples is shoma in Fig. 1. The i.t"(bo) plot is characteristic for granular high-T c superconductors, for which two distinct peaks are
bg-
m
,~ 0.10
i0.05 ~0.00
l
I0
bo[mT]
100
Fig. 1. Lossy component of magnetic permeability for nonhydrogenated (open symbols) and hydrogenated (full symbols) 1-2-3-type sample. commonly observed. The I~rst, low field peak, is related to the field value bm 1 at which the magnetic flux just reaches the centre of the sample (intergranular losses), whereas the maximum appearing at higher b o = bmg is related to losses in the grains. After hydrogenation of the sample the peak connected with the intergranular losses shifts to the lower value of b o (about three times lower), whereas the maximum connected x~ith intragrain losses shifts towards higher b o (an increase of about 28%). Employing critical state model of Bean one can estimate intergranular and intragranular critical current densities as 1.4x 106 A/m2 and 5× 109 A/m 2 respectively for non-hydrogenated sample and 4.7× 105 A/m 2 and 6.5× 109 A/m 2 respectively for hydrogenated one. Similar effect of increase of intragranular critical current density x~4th hydrogen doping was investigated in Lal.85Sr0.15CUO4 [3]. The existence of two different hydride phases in hydrogenated sample of Lal.85Sr0.15CuO 4 was confirmed by NMR measurements. The measurements were performed on a Bruker MSL 300S NMR spectrometer at a frequency of 300 MHz
0921-4534/94/$07.00 © 1994 - 'Elsevier Science B.V. All rights reserved.
SSD! 0921-4534(94)02086-8
bl
:Lo.16
3042
,7 Klamut et al./Pt~vsica C 2 3 5 240 (1994) 3041 3042
200
,,) ,,=o s'l;sx 100
,.i
gg 100
oo 50
-80
-40
0
40
80
u-u0[kHz ]
Fig.2. Fourier transform of NMR spectrum of H2Lal.85Sr0.15CUO4 (circles). Solid lies represent: L-Lorenzian component, G - Gaussian component, L+G - sum of Lorenzian and Gaussian components. and temperature of 294K. The NMR absorption spectra were obtained from the Fourier transform of the free induction decay ~4th phase cycling. Typically, 90 pulse was 3.5 ~,ts and the dead time of order 4 ~s. The 1H NMR spectra are shown in Fig. 2. The shape of the spectrum can be explained by superposition of two lines: x~de and narrow ones. We have used Gaussian and Lorentzian functions respectively for their description. The Gaussian component originates probably from the phase rich in hydrogen as the calculated second moment value is typical (m 2 = 0.1803 × (AVl/2) 2= 349 kHz 2) for transition metal hydrides in rigid-lattice regime. The second component, Lorentzian one, is relatively narrow and is specific for the systems ~.ith low hydrogen concentration and/or high mobilip,.' of hydrogen atoms [5]. Moessbauer Spectroscopy (MS) studies ~ere done on H0 4Lal ~9Sro l l(CUl_vFey)04 sample doped ~4th y=0.()05 ~7Fe, i n a ~tandard transmission geometry. Spectra taken st temperatures 30 - 300K are shown in Fig.3. Room Temperature (RT) MS spectrum consists of a unique quadrupole doublet as in the case of the nonhydrogenated sample. Below 280K this simple spectrum splits into two subspectra: nonmagnetic doublet with parameters similar to that observed at RT. and an additional magnetically split pattern. The ratio of intensities of magnetic (M) and nonmagnetic (NM) components does not change significantly below 200K and is approximately equal to IM/INM ~ 0.8. It is interesting that the Neel temperature of magnetic phase obtained from temperature dependence of hyperfine field at Fe-nucleus Hhf(T) is slightly lower
06 HiL61,|O'qrO.
04
i 0 ,
,
,
1 1 C1'1L04 i
,
i
,
i
-4 0 4 o velocity (ram/e)
Fig.3. M6ssbauer absorption spectra for La-Sr-Cu-O at room temperature and hydrogenated sample at different temperatures. than 280K, i.e. it is similar to the Neel temperature of sloichiometric insulating La2CuO 4. All above results suggest that the increase of pinning in hydrogenated 1-2-3-1ype and 2-1-4-tsqge materials is connected with the existence of normal, magnetic regions in the material induced by hydrogenatiou. This work was supported by KBN Grant No. 2-23-62-9203.
References
1.
2.
3.
4.
5.
J. J. Reilly, M. Suenaga, J. R. Johnson, P.Thompson. A.R.Moodenbaugh, Phys.Rev.B. 36 (1987) 5694: T.Kamiyama, S.Tomiyoshi, M.Omori, H. Yamauchi, T. Kajitani, T.Matsunaga, H.Yamamoto, Physica B. 148 (1987) 491. SD.Goren, C.Korn, V.Volterra, HRiesemeier. ERossler. MSchaefer. H.MVieth, K.Luders. Phvs.Rev. B, 42 (1990) 7949: Z.Heukie. T.Cichorek, HDrulis, JKlamut. Physica C, 214 (1993) 138. H. Drulis, J. Klamut, A. Zygmunt, N.M.Suleimanov. E.F.Kukovitskii, Solid Stale Commun., 84 (1992) 1069. MCiszek, JKiamut, A.J.Zaleski, H.Drulis, P.W.Klamut, J.Olejniczak, Journal of Applied Physics - in press B. Stalinski, C. K. Coogan, H. S. Gutowsky, J.Chem.Phys., 34 (1961) 1191; G.W.Canters, C.S.Johnson, J.Magn.Reson.. 6 (1972) 1.
Physica C 235-240 (1994)3041-3042 North-Holland
Increase o f pinning by hydrogenation in 1-2-3 and 2-1-4 types superconductors J.Klamut, M.Ciszek, H.Drulis, P.W.Klamut, K.Nied2wied2, B.Nowak, J.Olejniczak, A.J.Zaleski, O.J.Zogal, Institute of Low Temperatures and Structure Research, PAS. P.O.Box 937, 50-950 Wroclaw, Poland and International Laboratory, of High Magnetic Fields and Low Temperatures, Wroclaw, Poland Ac losses in ceramic Y-Ba-Cu-O and NMR and Mfssbauer studies of ceramic La-Sr-Cu-O superconductors before and after hydrogenation are presented. Two-phase behaviour of hydogenated samples, increased pinning and increased intragranular critical current density is evidenced. 1. Introduction
Almost immediately after the discovery of the high temperature superconductivity, works begun on the influence of hydrogenation on physical properties of this new class of superconductors. The first publications in this field appeared just in 1987 [1]. There is general agreement that introduction of hydrogen may reduce the number of holes (charge carriers in p-type high-T c ceramics) and that the material may become semiconducting and magnetic at high hydrogen concentrations. In 1-2-3 ~,pe superconductors the diminishing of ox.ygen content and increase of hydrogen content can act in similar way [2]. By hydrogenation non-superconducting regions may be created. These non superconducting inclusions can play the role of the pinning centers [3]. The above interpretation is in agreement xx~ith the results of investigation of the influence of hydrogen doping in YBa2Cu30 v on intragranular and intergranular critical currentg [4]. 2. Results and discussion
It is shown that introduction of hydrogen decreases the critical current between the grains simultaneously increasing the critical current inside the grains. On this basis a supposition was formulated stating that hydrogen weakens the Josephson links responsive for the intergranular currents while increasing pinning inside the grains, responsible for the intraganular critical current. The dependence of the lossy component g" of magnetic permeability for YBa2Cu30 7 on the external field anaplitude bo for non-hydrogenated and hydrogenated samples is shoma in Fig. 1. The i.t"(bo) plot is characteristic for granular high-T c superconductors, for which two distinct peaks are
bg-
m
,~ 0.10
i0.05 ~0.00
l
I0
bo[mT]
100
Fig. 1. Lossy component of magnetic permeability for nonhydrogenated (open symbols) and hydrogenated (full symbols) 1-2-3-type sample. commonly observed. The I~rst, low field peak, is related to the field value bm 1 at which the magnetic flux just reaches the centre of the sample (intergranular losses), whereas the maximum appearing at higher b o = bmg is related to losses in the grains. After hydrogenation of the sample the peak connected with the intergranular losses shifts to the lower value of b o (about three times lower), whereas the maximum connected x~ith intragrain losses shifts towards higher b o (an increase of about 28%). Employing critical state model of Bean one can estimate intergranular and intragranular critical current densities as 1.4x 106 A/m2 and 5× 109 A/m 2 respectively for non-hydrogenated sample and 4.7× 105 A/m 2 and 6.5× 109 A/m 2 respectively for hydrogenated one. Similar effect of increase of intragranular critical current density x~4th hydrogen doping was investigated in Lal.85Sr0.15CUO4 [3]. The existence of two different hydride phases in hydrogenated sample of Lal.85Sr0.15CuO 4 was confirmed by NMR measurements. The measurements were performed on a Bruker MSL 300S NMR spectrometer at a frequency of 300 MHz
0921-4534/94/$07.00 © 1994 - 'Elsevier Science B.V. All rights reserved.
SSD! 0921-4534(94)02086-8
bl
:Lo.16
3042
,7 Klamut et al./Pt~vsica C 2 3 5 240 (1994) 3041 3042
200
,,) ,,=o s'l;sx 100
,.i
gg 100
oo 50
-80
-40
0
40
80
u-u0[kHz ]
Fig.2. Fourier transform of NMR spectrum of H2Lal.85Sr0.15CUO4 (circles). Solid lies represent: L-Lorenzian component, G - Gaussian component, L+G - sum of Lorenzian and Gaussian components. and temperature of 294K. The NMR absorption spectra were obtained from the Fourier transform of the free induction decay ~4th phase cycling. Typically, 90 pulse was 3.5 ~,ts and the dead time of order 4 ~s. The 1H NMR spectra are shown in Fig. 2. The shape of the spectrum can be explained by superposition of two lines: x~de and narrow ones. We have used Gaussian and Lorentzian functions respectively for their description. The Gaussian component originates probably from the phase rich in hydrogen as the calculated second moment value is typical (m 2 = 0.1803 × (AVl/2) 2= 349 kHz 2) for transition metal hydrides in rigid-lattice regime. The second component, Lorentzian one, is relatively narrow and is specific for the systems ~.ith low hydrogen concentration and/or high mobilip,.' of hydrogen atoms [5]. Moessbauer Spectroscopy (MS) studies ~ere done on H0 4Lal ~9Sro l l(CUl_vFey)04 sample doped ~4th y=0.()05 ~7Fe, i n a ~tandard transmission geometry. Spectra taken st temperatures 30 - 300K are shown in Fig.3. Room Temperature (RT) MS spectrum consists of a unique quadrupole doublet as in the case of the nonhydrogenated sample. Below 280K this simple spectrum splits into two subspectra: nonmagnetic doublet with parameters similar to that observed at RT. and an additional magnetically split pattern. The ratio of intensities of magnetic (M) and nonmagnetic (NM) components does not change significantly below 200K and is approximately equal to IM/INM ~ 0.8. It is interesting that the Neel temperature of magnetic phase obtained from temperature dependence of hyperfine field at Fe-nucleus Hhf(T) is slightly lower
06 HiL61,|O'qrO.
04
i 0 ,
,
,
1 1 C1'1L04 i
,
i
,
i
-4 0 4 o velocity (ram/e)
Fig.3. M6ssbauer absorption spectra for La-Sr-Cu-O at room temperature and hydrogenated sample at different temperatures. than 280K, i.e. it is similar to the Neel temperature of sloichiometric insulating La2CuO 4. All above results suggest that the increase of pinning in hydrogenated 1-2-3-1ype and 2-1-4-tsqge materials is connected with the existence of normal, magnetic regions in the material induced by hydrogenatiou. This work was supported by KBN Grant No. 2-23-62-9203.
References
1.
2.
3.
4.
5.
J. J. Reilly, M. Suenaga, J. R. Johnson, P.Thompson. A.R.Moodenbaugh, Phys.Rev.B. 36 (1987) 5694: T.Kamiyama, S.Tomiyoshi, M.Omori, H. Yamauchi, T. Kajitani, T.Matsunaga, H.Yamamoto, Physica B. 148 (1987) 491. SD.Goren, C.Korn, V.Volterra, HRiesemeier. ERossler. MSchaefer. H.MVieth, K.Luders. Phvs.Rev. B, 42 (1990) 7949: Z.Heukie. T.Cichorek, HDrulis, JKlamut. Physica C, 214 (1993) 138. H. Drulis, J. Klamut, A. Zygmunt, N.M.Suleimanov. E.F.Kukovitskii, Solid Stale Commun., 84 (1992) 1069. MCiszek, JKiamut, A.J.Zaleski, H.Drulis, P.W.Klamut, J.Olejniczak, Journal of Applied Physics - in press B. Stalinski, C. K. Coogan, H. S. Gutowsky, J.Chem.Phys., 34 (1961) 1191; G.W.Canters, C.S.Johnson, J.Magn.Reson.. 6 (1972) 1.