Strong antiferromagnetic proximity coupling in a heterostructured superconductor Sr2VO3FeAs
Abstract
We report observation of strong magnetic proximity coupling in a heterostructured superconductor Sr2VO3FeAs, determined by the upper critical fields Hc2(T) measurements up to 65 T. Using the resistivity and the radio-frequency measurements for both H ab and H c, we found a strong upward curvature of Hc2c(T), together with a steep increase of Hc2ab(T) near Tc, yielding the anisotropic factor γH=Hc2ab/Hc2c up to 20, the largest value among iron-based superconductors. These are attributed to the Jaccarino-Peter effect, rather than to the multiband effect, due to strong exchange interaction between itinerant Fe spins of the FeAs layers and localized V spins of Mott-insulating SrVO3 layers. These findings provide evidence for strong antiferromagnetic proximity coupling, comparable with the intralayer superexchange interaction of SrVO3 layer and sufficient to induce magnetic frustration in Sr2VO3FeAs.