PHYSICAL REVIEW B 82, 174439 (2010); DOI: 10.1103/PhysRevB.82.174439
Using polarized neutron reflectometry we investigated the reversal of the magnetization of a high-Tc superconductor/ferromagnet superlattice that consists of eight bilayers of YBa2Cu3O7(25.6 nm) /La2/3Ca1/3MnO3(25.6 nm) grown on a SrTiO3 substrate. The measurements were performed during a magnetization hysteresis loop at 5 K. We obtained evidence that the reversal in the vicinity of the coercive field proceeds via the switching of micrometer-sized magnetic domains that are considerably larger than the typical domains of La2/3Ca1/3MnO3. Furthermore, these large magnetic domains appear to be more strongly correlated along the vertical direction of the superlattice than along the lateral one. We provide evidence that this unusual behavior may be induced by the SrTiO3 substrate which undergoes a series of structural phase transitions, some of which give rise to the formation of micrometer-sized surface facets that are tilted with respect to each other. These facets and the resulting strain fields are transmitted throughout the superlattice and thus may act as templates for the large magnetic domains in the La2/3Ca1/3MnO3 layers whose magnetic properties are very susceptible to the lattice strain.
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