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Haberkorn, N., J. Guimpel, M. Sirena, L. B. Steren, W. Saldarriaga, E. Baca, and M. E. Gomez. "Antiferromagnetism at the YBa2Cu3O7/La2/3Ca1/3MnO3 interface." Applied Physics Letters 84, no. 19 (2004): 3927–3929.
Abstract: The magnetic properties of a series of YBa2Cu3O7-x/La2/3Ca1/3MnO3 (YBCO/LC1/3MO) superlattices grown by dc sputtering at high oxygen pressures (3.5 mbar) show the expected ferromagnetic behavior. However, field-cooled hysteresis loops at a low temperatures show the unexpected existence of exchange bias effect associated with the existence of ferromagnetic/antiferromagnetic (AF) interfaces. The blocking temperature (T-B) is found to be thickness dependent and the exchange bias field (H-EB) is found to be inversely proportional to the ferromagnetic layer thickness, as expected. The presence of an AF material is probably associated with interface disorder and Mn valence shift toward Mn4+. (C) 2004 American Institute of Physics.
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Haberkorn, N., J. Guimpel, M. Sirena, L. B. Steren, G. Campillo, W. Saldarriaga, and M. E. Gomez. "Interface disorder and transport properties in HTC/CMR superlattices." PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 408 (2004): 896–897.
Abstract: The physical properties of superlattices are affected by interface disorder, like roughness and interdiffusion. X-ray diffraction allows its measurement through modeling and structure refinement. The high-T-c RBa2Cu3O7 (RBCO) and colossal magneto resistance La(x)A(1-x)MnO(3) (LAMO) perovskites are interesting superlattice partners given their similar lattice parameters and because the combination of magnetic and superconducting properties is interesting for both basic and applied research. We have investigated the structural and transport properties of YBCO/La2/3Ca1/3MnO3 and GdBCO/La0.6Sr0.04MnO3 superlattices grown by sputtering on (100)MgO. We find a roughness of 1 RBCO unit cell and a 30% interdiffusion in the same length from the interfaces for all samples. The superconducting behavior is found strongly dependent on the LAMO layer thickness. (C) 2004 Elsevier B.V. All rights reserved.
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Guimpel, J., N. Haberkorn, M. Sirena, L. B. Steren, W. Saldarriaga, E. Baca, and M. E. Gomez. "Interface effects in perovskite superlattices." JOURNAL OF LOW TEMPERATURE PHYSICS 135, no. 1-2 (2004): 115–118.
Abstract: The effect of interface disorder in perovskite superlattices, either with the substrate or between layers dominates the physics of the material, even when the lattice parameter of the component materials differs in less than 1%. Unexpected behavior emerges, like exchange bias in a system where no antiferromagnetic material has been included in the superlattice design.
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Haberkorn, N., J. Guimpel, L. B. Steren, G. Campillo, W. Saldarriaga, and M. E. Gomez. "Structure of high-T-c/manganite perovskite superlattices." JOURNAL OF APPLIED PHYSICS 94, no. 5 (2003): 3011–3014.
Abstract: We study the crystalline and interface structure of RBa2Cu3O7/La(1-x)A(x)MnO(3) superlattices (R=Y, Gd; A=Ca, Sr) grown on mismatched MgO substrates by means of nondestructive x-ray diffraction. The diffraction patterns are adjusted to a model of the structure which includes interface roughness and interdiffusion. Our results show that these disorder mechanisms cannot be neglected and should be taken into account to understand the physical properties of these superlattice. (C) 2003 American Institute of Physics.
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