Tunable competition and possible coexistence between superconductivity and ferromagnetism in the multilayers of YBa2Cu3O7−δ/La0.67Sr0.33MnO3

Multilayers consisting of superconducting YBa2Cu3O7−δ (YBCO) and ferromagnetic La0.67Sr0.33MnO3 (LSMO), namely p×(YBCO(m)/LCMO(n)) (p: repetition periods, m: number of YBCO unit cell, and n: number of LSMO unit cell) are prepared on single crystal SrTiO3 (STO) substrates by pulsed laser deposition (PLD), with a view to understand the competition and coexistence between superconductivity and ferromagnetism. The present multilayers show suppressed superconductivity and all kinks of magnetic hysteresis loops, which is subject to the thicknesses of the constituent layers and the temperature. This reflects the complicated interactions of different length scales at YBCO/LSMO interfaces. In the multilayer with extremely thinner unit layer thickness, the in-plane and out-of-plane hysteresis loops show dual features from superconducting and ferromagnetic components, maybe an indication of coexistence of superconductivity and ferromagnetism which originates from the superconducting proximity effect.