Single crystals of Y1-xDyxΝi2B2C (1 ≤ x≤ 0.7) were examined by
X-ray diffraction and stoichiometry was attested by XPS measurements. The
superconducting transition temperature T^ and Neel temperature TN were
determined by means of magnetisation measurements. A dramatic breakdown
of the de Gennes scaling in the Dy-rich compounds was found when
< TN

Drzazga, Zofia

Kaczorowski, D.

Winiarska, Anna

Winiarski, Antoni

Acta Physica Polonica A

English

Repozytorium Uniwersytetu Śląskiego RE-BUŚ

             Title: Breakdown of the de Gennes scaling in Y1-xDyxNi2B2C    Author: Zofia Drzazga, Anna Winiarska, Antoni Winiarski, D. Kaczorowski    Citation style: Drzazga Zofia, Winiarska Anna, Winiarski Antoni, Kaczorowski D. (2000). Breakdown of the de Gennes scaling in Y1-xDyxNi2B2C. "Acta Physica Polonica. A" (Vol. 97, nr 1 (2000), s. 221-224). Vol. 97 (2000)	 A CtA PHYSICA POLONICA A 	 No. 1Proceedings of the European Conference "Physics of Magnetism '99", Poznań 1999BREAKDOWN OF THE DE GENNES SCALINGIN Υ1- x Dyx Νi 2B2 CZ. DRZAZGA, A. WINIARSKA, A. WINIARSKIInstitute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice, PolandAND D. KACZOROWSKIInstitute of Low Temperature and Structure Research, Polish Academy of SciencesP.O. Box 937, Wrocław 2, PolandSingle crystals of Y1-xDyxΝi2B2C (1 ≤ x≤  0.7) were examined byX-ray diffraction and stoichiometry was attested by XPS measurements. Thesuperconducting transition temperature T^ and Neel temperature TN weredetermined by means of magnetisation measurements. A dramatic break-down of the de Gennes scaling in the Dy-rich compounds was found when< TN.PACS numbers: 74.25.Ηa, 74.72.-h, 82.80.Pν1. IntroductionThe physical properties of RNi2Β2C, where R = Y, Lu or rare earth, havebeen the subject of many recent studies [1-3]. The structure of these compounds isa body-centred tetragonal ThCr2Sí2-type structure with additional carbon atomsin the rare earth plane. Superconductivity is observed for non-magnetic elementsLu and Y as well as for heavy magnetic rare earth. The superconducting transitiontemperature T^ decreases across the RΝi 2 Β 2 C series with the de Gennes factordG = (g — 1) 2 J(J + 1), where g is the Landé factor and J is the total angularmomentum of the R+3 Hund rule ground states [2]. Good overall de Gennes scalingfor the antiferromagnetic ordering Neel temperature TN is also reported. Theseresults reveal a coupling between the conduction electrons and the local magneticmoments of rare earth due to the long range s— f interactions in the RNi2Β2Ccompounds. In the pseudoquaternary Rx RΝi2Β2C, where R' is Y, Lu or theother rare earth, a more complicated correlation between T^ and TN is observed. .In the compounds diluted by a non-magnetic element a deviation from the deGennes scaling depends on the rare earth [4, 5]. Therefore, in this work the scalingbehaviour of Tc and TN for single crystals of Y1-xDy Νi2Β2C has been studied.(221)222 	 Z. Drzazga et al.2. Experimental and resultsY1-xDyNi2B2C compounds were prepared by arc melting of high purityconstituents and next by prolonged annealing at 920°C for one week. Good qualityplates like crystals with dimensions of about 1 x 1 x 0.1 mm 3 have been extractedfrom the samples. The crystals were examined with X-ray diffraction. The XPSmeasurements were carried out with a multítechnique electron spectrometer PHI5700/660 from Physical Electronics on broken, scraped or sputtered samples. Themagnetic measurements were carried out as a function of external magnetic fieldup to 5 T in the temperature range 1.7-300 K using a SQUID magnetometer.Fig. 1. (a) Overlapping the Y 3d and Dy 4d photoelectron spectra, (b) B s spectra ofYxDy1—xNi2B2C.The atomic concentrations of the investigated samples were calculated fromthe XPS spectra using the PHI program. Overlapped features of Y 3d and Dy 4d(Fig. 1a) as well as Y 3p and Dy 4/33 2 were separated to calculate the contributionof each feature to the measured spectra. The atomic concentrations of Y, Dy, Ni,and C were found to be close to those which were assumed from technology. Insome samples a certain fluctuation of the boron content was noticed. The B 1sspectra obtained at various conditions are displayed in Fig. 1b. An additionalweak broad feature at 192.3 eV observed in some B 1s spectra can be caused bysputtering the samples or indicates a deficit of B in its crystallographic positions.A temperature dependence of the magnetic susceptibility measured in ex-ternal field of H = 50 Oe and 1000 Oe is presented in Fig. 2. At the lowesttemperatures a diamagnetic signal was observed in magnetic field of H = 50 OeBreakdown of the de Gennes Scalng in Υ1-xDyNi2B2C	 223Fig. 2. Temperature dependence of dc magnetic susceptibility measured in variousmagnetic fields.Fig. 3. Τ and TN versus xdG(R+3 ) for Y1—xDyxNi2B2C.for zero- field cooled samples. Superconductivity was detected for all studied con-centrations but the shielding effect was weak, presumably because the applied fieldwas of the order of the first flux penetration field [3]. Moreover, superconductingproperties of these compounds are known to be sensitive to the stoichiemetry ofthe samples [6]. Temperature in which the diamagnetic contribution vanishes inZFC plots has been taken as a superconducting transition temperature. However,on cooling in the same field (50 Oe), the FC plots show an anomalous behaviour,with positive values below Τ. This positive contribution in the superconductingstate appears probably due to the ordering of the Dy moments above  Τ. Param-agnetic Meissner effect was reported earlier for ceramic Βi 2 Sr2 CaCu 2 Ox supercon-ductors [7]. The origin of the paramagnetic Meissner effect in the high-Τc cupratescould be spontaneous orbital current and the weak-link Josephson junctions or apinning effect in the Kosterlitz—Thouless transition [8]. Furthermore, the dilutionof the magnetic Dy sublattice by the non-magnetic Y atoms may enhance thisunusual effect.The temperature dependence of the dc susceptibility observed at 1 kOeshowed the characteristic peak at TN due to antíferromagnetíc ordering (Fig. 2).A comparison of the χ(T) plots proves a coexistence of superconductivity andmagnetism for these compounds for Τc < TN as well as for Τ > TN. Figure 3displays Τ^ and TN versus the effective de Gennes factor xdG(R+3), where x is theconcentration of the magnetic ions in Y 1-xDyNi2B 2 C. A deviation from the linearscaling of the superconducting transition temperature Τc is observed. A breakdownof scaling is clearly seen for Dy concentration x> 0.5 while a rather good param-eterisation of magnetic pair breaking for x < 0.5 is found. For Y-rich samples Τ^224 	 Z. Drzazga et ad.is suppressed nearly linearly with xdG according to Abrikosov—Gorkov theory. Inthe case of the Dy-rich samples changes in Τc are more complicated. In turn, TNdecreases gradually with an increase in nonmagnetic atoms. The non-magnetic cen-tres could be theoretically conjectured to influence Τc due to destruction transla-tion symmetry of antiferromagrietic dysprosium lattice [5]. On the other hand, col-lective magnetic excitations could be responsible for pair breaking when Τc < TNanalogously as in Ho1-xDyNi2B2C [4].A more detailed analysis of interplay between superconductivity and mag-netism will be published elsewhere.AcknowledgmentsThe multitechnique electron spectrometer PHI 5700/660 was partially sup-port by the Foundation for Polish—German Cooperation, the Committee for Sci-entific Research and FNP-SUBIN 95 program.References[1] R.J. Cava, H. Takagi, H.W. Zandbergen, J.J. Krajewski, W.F. Peck Jr., T. Siegri-est, B. Batlogg, R.B. van Dover, R.J. Felder, K. Mizuhcrsi, J.O. Lee, H. Elisaki,S. Uchida, Nature 367, 252 (1994).[2] H. Élisaki, H. Takagi, R.J. Cava, B. Batlogg, J.J. Krajewskí, W.F. Peck Jr.,K. Mizuhasi, J.O. Lee, S. Uchida, Phys. Rew. Β 50, 647 (1994).[3] R. Szymczak, M .Baran, L. Gladczuk, H. Szymczak, Z. Drzazga, A. Winiarska,Physica C 254, 124 (1995).[4] B.K. Cho, P.C. Canfield, D.C. Johnston, Phys. Rew. Lett. 77, 163 (1996).[5] Z. Hossain, R. Nagarajan, S.K. Dhar, L.C. Gupta, Physics Β 259-261, 606 (1999).[6] C.V. Tory, G. Balakrishan, D.McK. Paul, Physics C 248, 349 (1995).[7] W. Braunisch, N. Knauf, V. Kataev, S. Neuhausen, A. Grutz, A. Kock, B. Roden,D. Khomski, D. Wöhlleben, Phys. Rew. Lett. 68, 1908 (1992).[8] P. Svendlindh, K. Niskanane, P. Norling, P. Nordblad, L. Lundgren, B. Lonnberg,T. Lundstrom, Physica C 162-164, 1365 (1989).

Breakdown of the de Gennes scaling in Y1-xDyxNi2B2C

https://rebus.us.edu.pl/bitstream/20.500.12128/8505/1/Drzazga_Breakdown_of_the_de_Gennes_scaling.pdf

Breakdown of the de Gennes scaling in Y1-xDyxNi2B2C

Abstract

Similar works

Full text

Available Versions

Repozytorium Uniwersytetu Śląskiego RE-BUŚ