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Pastoriza, H.; Candia, S.; Nieva, G. |
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Title  |
Anisotropic vortex dynamics in twined YBaCuO single crystals |
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2000 |
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Physica B |
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284-288 |
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2 |
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763-764 |
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Rotating continuously the applied vortex force and measuring the vortex velocity vector, we were able to directly determine the role of twin boundaries in the vortex dynamics in YBa$2$Cu$3Ο_7$ single crystals with unidirectional twins. We show the different effect of these correlated pinning defects into the various vortex phases. In the entangled vortex liquid state, we observe a linear response but with an anisotropic viscosity. On the other hand, an anomalous guided motion by twin planes is found in the vortex solid. |
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BT @ hernan @ pastoriza00 |
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39 |
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Fainstein, A.; Maiorov, B.; Guimpel, J.; Nieva, G.; Osquiguil, E. |
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Title |
Annealing disorder and photoinduced order of oxygen chains in detwinned YBa2Cu3O6.65 single crystals probed by Raman scattering |
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Journal Article |
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Year |
2000 |
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Physical Review B – Condensed Matter and Materials Physics |
Abbreviated Journal |
Phys. Rev. B Condens. Matter Mater. Phys. |
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61 |
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6 |
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4298-4304 |
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Raman scattering in detwinned YBa2Cu3O6.65 single crystals is studied as a function of photoexcitation and annealing. Copper-oxygen chain-related forbidden Raman bands that are known to strongly bleach with illumination at low temperatures, increase their intensity with chain fragmentation induced by annealing at high temperature. This contrasting behavior proves the conjunction of short Cu-O fragments into longer chains on photoexcitation. We interpret the Raman modes as due to vibrations at the end of CuO chain fragments and Cu-O-Cu monomers, and use their evolution with illumination and annealing as anisotropic sensitive markers of oxygen reordering processes. The identification of the “forbidden” Raman bands is discussed in the context of our results and recent literature in the subject. We also present absorption measurements performed on GdBa2Cu3Ox thin films with varying oxygen content. These experiments show that the 2.2-eV absorption and the chain-related Raman peaks have different dependencies with oxygen content and illumination, ruling out an explanation that suggests that the Raman intensity reduction of these modes is due to a photobleaching of intermediate defect states. These results highlight the potentialities of Raman scattering for oxygen dynamics studies and demonstrate the presence of photoinduced oxygen ordering in these high-Tc superconductor compounds. |
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01631829 (ISSN) |
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Cited By (since 1996): 18; Export Date: 17 April 2009; Source: Scopus; CODEN: PRBMD; Language of Original Document: English; Correspondence Address: Fainstein, A.; Centro At |
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BT @ osquigui @ |
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374 |
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Decca, R.S.; Drew, H.D.; Osquiguil, E.; Maiorov, B.; Guimpel, J. |
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Title |
Anomalous proximity effect in underdoped YBa2Cu3O6+x Josephson junctions |
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Journal Article |
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Year |
2000 |
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Physical Review Letters |
Abbreviated Journal |
Phys Rev Lett |
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Volume |
85 |
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17 |
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3708-3711 |
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Keywords |
Critical currents; Energy gap; High temperature superconductors; Magnetic field effects; Magnetron sputtering; Mathematical models; Phase diagrams; Phase transitions; Physical properties; Scanning electron microscopy; Superconductivity; Yttrium barium copper oxides; Anomalous proximity effect; Fluctuating phase models; Josephson effect; Photodoping; Josephson junction devices |
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Experiments were carried out to probe the underdoped insulating material by the Josephson effect. Junctions were fabricated by exploiting the capability of locally photodoping insulating RBa2Cu3O6+x (R = rare earth) material. The existence of an anomalously large proximity effect was confirmed. The critical current of the junctions was consisted with the conventional Josephson relationship. |
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American Inst of Physics |
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Woodbury, NY, United States |
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00319007 (ISSN) |
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Cited By (since 1996): 36; Export Date: 17 April 2009; Source: Scopus; CODEN: PRLTA; doi: 10.1103/PhysRevLett.85.3708; Language of Original Document: English; Correspondence Address: Decca, R.S.; Univ of Maryland College Park, United States; References: Ginsberg, D.M., (1996) Physical Properties of High Temperature Superconductors V, , World Scientific, Singapore; Zhang, S.C., (1997) Science, 275, p. 1089; Emery, V.J., Kivelson, S.A., (1995) Nature (London), 374, p. 434; Corson, J., (1999) Nature (London), 398, p. 291; Renner, Ch., (1998) Phys. Rev. Lett., 80, p. 149; Demler, E., (1998) Phys. Rev. Lett., 80, p. 2917; Den Hertog, B.C., Berlinsky, A.J., Kallin, C., (1999) Phys. Rev. B, 59, pp. R11645; Emery, V.J., Kivelson, S.A., Zachar, O., (1997) Phys Rev. B, 56, p. 6120; Tinkham, M., (1996) Introduction to Superconductivity, , McGraw-Hill, New York; Decca, R.S., (1998) Appl. Phys. Lett., 73, p. 120; (1999) J. Microsc., 194, p. 407; Osquiguil, E., (1992) Appl. Phys. Lett., 60, p. 1627; Kudinov, V.I., (1993) Phys. Rev. B, 47, p. 9017; Decca, R.S., Drew, H.D., Empson, K.L., (1997) Appl. Phys. Lett., 70, p. 1932; Orenstein, J., (1990) Phys. Rev. B, 42, p. 6342; Nieva, G., (1992) Appl. Phys. Lett., 60, p. 2159; (1992) Phys. Rev. B, 46, p. 14249; notenoteGray, K.E., (1992) Phys. Rev. B, 45, p. 10071; Pauza, A.J., (1997) J. Appl. Phys., 82, p. 5612; Katz, A.S., Woods, S.I., Dynes, R.C., (2000) J. Appl. Phys., 87, p. 2978; noteUR – http://www.scopus.com/scopus/inward/record.url?eid=2-s2.0-19244384844&partnerID=40 |
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BT @ osquigui @ |
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373 |
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Jaime, M.; Movshovich, R.; Stewart, G.R.; Beyermann, W.P.; Berisso, M.G.; Hundley, M.F.; Canfield, P.C.; Sarrao, J.L. |
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Title |
Closing the spin gap in the Kondo insulator Ce3Bi4Pt3 at high magnetic fields |
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Journal Article |
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Year |
2000 |
Publication |
Nature |
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Volume |
405 |
Issue |
6783 |
Pages |
160-163 |
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Kondo insulator materials(1)-such as CeRhAs, CeRhSb, YbB12, Ce3Bi4Pt3 and SmB6-are 3d, 4f and 5f intermetallic compounds that have attracted considerable interest in recent years(2-5). At high temperatures, they behave like metals. But as temperature is reduced, an energy gap opens in the conduction band at the Fermi energy and the materials become insulating. This contrasts with other f-electron compounds, which are metallic at all temperatures. The formation of the gap in Kondo insulators has been proposed to be a consequence of hybridization between the conduction band and the f-electron levels(6,7), giving a 'spin' gap. If this is indeed the case, metallic behaviour should be recovered when the gap is closed by changing external parameters, such as magnetic field or pressure. Some experimental evidence suggests that the gap can be closed in SmB6 (refs 5, 8) and YbB12 (ref. 9). Here we present specific-heat measurements of Ce3Bi4Pt3 in d.c. and pulsed magnetic fields up to 60 tesla. Numerical results and the analysis of our data using the Coqblin-Schrieffer model demonstrate unambiguously a field-induced insulator-to-metal transition. |
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0028-0836 |
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ISI:000087080100043 |
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BT @ hernan @ |
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300 |
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Herbsommer, Juan A. |
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Title |
Dinámica y estática de vórtices en superconductores de alta temperatura crítica con defectos correlacionados |
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Book Whole |
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2000 |
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Instituto Balseiro |
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Ph.D. thesis |
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328 |
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Sereni, J.G. |
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Title |
Evanescence of magnetic transitions in Ce systems |
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2000 |
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Physica B – Condensed Matter |
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Physica B |
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281-282 |
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337-339 |
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Three types of magnetic phase diagrams can be identified in Ce systems: (I) with ordering temperature T-ord --> 0 continuously, followed by a narrow non-Fermi-liquid (NFL) region, (II) with T-ord vanishing at finite temperature, followed by an extended NFL region, and (III) where the degrees of freedom condensed into the ordered phase decreases, without a concomitant decrease of T-ord. Intrinsic differences are found in the way that the degrees of freedom condense at T-ord and from the rising of the specific heat tails above T-ord. (C) 2000 Elsevier Science B.V. All rights reserved. |
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0921-4526 |
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ISI:000086570200141 |
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BT @ hernan @ |
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79 |
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Maiorov, B.; Nieva, G.; Osquiguil, E. |
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Title |
First-order phase transition of the vortex lattice in twinned YBa2Cu3O7 single crystals in tilted magnetic fields |
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Journal Article |
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2000 |
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Physical Review B – Condensed Matter and Materials Physics |
Abbreviated Journal |
Phys. Rev. B Condens. Matter Mater. Phys. |
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61 |
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18 |
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12427-12432 |
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We present an exhaustive analysis of transport measurements performed in twinned YBa2Cu3O7 single crystals which establishes that the vortex solid-liquid transition is first order when the magnetic field H is applied at an angle ? away from the direction of the twin planes. We show that the resistive transitions are hysteretic and the V-I curves are nonlinear, displaying a characteristic S shape at the melting line Hm(T), which scales as ?(?)Hm(T,?), where ?(?) is the anisotropy factor. These features are gradually lost when the critical point H*(?) is approached. Above H*(?) the V-I characteristics show a linear response in the experimentally accessible V-I window, and the transition becomes reversible. Finally we show that the first-order phase transition takes place between a highly correlated vortex liquid in the field direction and a solid state of unknown symmetry. As a consequence, our data support the scenario for a vortex-line melting in twinned YBa2Cu3O7 crystals in contrast to a vortex sublimation as recently suggested for untwinned La2-xSrxCuO4, YBa2Cu3O7 and Bi2Sr2CaCu2O8 [T. Sasagawa et al., Phys. Rev. Lett. 80, 4297 (1998)]. |
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01631829 (ISSN) |
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Cited By (since 1996): 5; Export Date: 17 April 2009; Source: Scopus; CODEN: PRBMD; Language of Original Document: English; Correspondence Address: Maiorov, B.; Centro At |
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BT @ osquigui @ |
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372 |
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Roa Rojas, J.; Jurelo, A.R.; Menegotto Costa, R.; Mendonca Ferreira, L.; Pureur, P.; Orlando, M.T.D.; Prieto, P.; Nieva, G. |
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Fluctuation conductivity and the dynamical universality class of the superconducting transition in the high-Tc cuprates |
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Journal Article |
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2000 |
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Physica C: Superconductivity |
Abbreviated Journal |
Physica C |
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341-348 |
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3 |
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1911-1912 |
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Systematic measurements of the fluctuation conductivity in several high-temperature superconducting cuprates show the occurrence of a genuine critical regime. The conductivity exponent is consistent with the predictions of the 3D-XY universality class and yields a dynamical critical exponent z = 1.5. |
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0921-4534 |
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ISI:000165855900185 |
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BT @ hernan @ |
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223 |
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Herbsommer, J.A.; Nieva, G.; Luzuriaga, J. |
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Interaction of vortices with oriented twin boundaries in single-crystal YBa2Cu3O7-delta |
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Journal Article |
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2000 |
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Physical Review B |
Abbreviated Journal |
Phys. Rev. B |
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61 |
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17 |
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11745-11751 |
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We have studied the response of the vortex lattice (VL) in a YBa2Cu3O7-delta sample with oriented twin boundaries (TB's) and in an untwinned sample. In the twinned sample the density of twin boundaries is estimated from decoration experiments. The TB's affect the liquid-to-solid transition in the vortex structure, which is of first order in the twin free crystal and to a Bose glass in the twinned sample. We measure the ac susceptibility, and find that the response strongly depends on the orientation of the probing ac field with respect to the TB's. The ac field produces a tilting stress on the vortices. With the applied de magnetic field H-dc parallel to the c axis, the response of the VL is weaker when the tilt is parallel to the TB's than when it is perpendicular or at 45 degrees to the TB's. The results are explained by the fact that the VL is locked to the twin boundaries for small deviations of H-dc from the c axis and is partially pinned to them for larger angles. By measuring over the whole angular range we estimate the angles over which each regime is realized for different temperatures. The results of the detwinned sample are used for comparison. |
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1098-0121 |
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ISI:000086937700090 |
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BT @ hernan @ |
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228 |
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Herbsommer, J.A.; Nieva, G.; Luzuriaga, J. |
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Interplay between pinning energy and vortex interaction in YBa2Cu3O7-delta with oriented twin boundaries in tilted magnetic fields: Bitter decoration and tilt-modulus measurements |
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Journal Article |
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2000 |
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Physical Review B |
Abbreviated Journal |
Phys. Rev. B |
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62 |
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5 |
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3534-3541 |
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We have performed Bitter decoration and ac susceptibility measurements in single-crystal YBa2Cu3O7-delta with oriented twin boundaries. The twin boundaries (TB's) pin vortices over approximately 65% of the sample. The pinned areas are unevenly distributed and some relatively large TB-free regions are present. The Bitter decorations were performed in a 52 Oe de magnetic field rotated off the c axis so that the plane defined by the field direction and the c axis is perpendicular to the TB's. Several decorations were performed in the same sample. Additional dynamical information was obtained from ac susceptibility measurements. Results show that for small tilts the vortices remain locked to the c-axis direction, for angles greater than 12 degrees they form a staircase pattern, and in this case pinning by the twin boundaries remains effective up to 75 degrees. We observe vortex chains in twin-free-zones of the sample for tilted fields at 65 degrees and 40 degrees. Due to our particular experimental arrangement, in the twinned regions the interplay of the potentials giving rise to the chains and the pinning potential produces a structure with a disordered square symmetry. The data allow us to estimate the dominant energy of the vortex system for some inclinations of the applied magnetic field. |
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0163-1829 |
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ISI:000088714200086 |
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BT @ hernan @ |
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224 |
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