Magnetic proximity effect in perovskite superconductor/ferromagnet multilayers

Abstract

YBa2Cu3O7/La 2/3 Ca 1/3 MnO3 superconducting/ferromagnetic (SC/FM) multilayers have been studied by neutron reflectometry. Evidence for a characteristic difference between the structural and magnetic depth profiles is obtained from the occurrence of a structurally forbidden Bragg peak in the FM state. The comparison with simulated reflectivity curves allows us to identify two possible magnetization profiles: a sizable magnetic moment within the SC layer antiparallel to the one in the FM layer (inverse proximity effect), or a "dead" region in the FM layer with zero net magnetic moment. The former scenario is supported by an anomalous SC-induced enhancement of the offspecular reflection, which testifies to a strong mutual interaction of SC and FM order parameters.

Depth profile of the ferromagnetic order in a YBa2Cu3O7/LaUribe-Laverde1, Satapathy2, Marozau3 et al. 2013Phys. Rev. BSelf Cite

“…As was the case in Ref. 25, it may still happen that different models lead to similar results and therefore cannot be distinguished. As shown below, this ambiguity might be overcome with reflectivity curves that extend up to larger q z values where the differences between the various models become more pronounced.…”

“…PNR measurements on SLs with equally thick YBCO and LCMO layers, for which the even order superlattice Bragg-peaks should be absent for symmetry reasons, showed that a 2nd order Bragg peak appears and gains considerable intensity below the FM transition, T Curie , of the LCMO layers 25 . This observation clearly showed that the depth profile of the magnetic potential has a lower local symmetry than the nuclear one.…”

“…Two different models were proposed in Ref. 25 to describe this magnetic proximity effect: a so-called "dead layer model" with a strongly reduced magnetization on the LCMO side, and a so-called "inverse proximity effect model" where ferromagnetic Cu moments antiparallel to the Mn moments in LCMO are induced on the YBCO side of the interface. It was not possible to distinguish between these two possibilities since the PNR data contained only a fairly limited range in momentum space such that the superlattice Bragg peaks beyond the 2nd order were not observed.…”

Crossover from magnetostatic to exchange coupling in La0.67Ca0.33MnO3/YBa2Cu3O7/La0.67Ca0.33MnO3heterostructures

“…A variety of novel phenomena like spin triplet superconductivity [5][6][7][8], superconducting spin switch [9][10][11][12], and vortex pinning by magnetic domain wall interactions [13] have been reported in them. Besides, the T C modulation of the S-layer in the presence of F-layer, the contrasting magnetic nature of S/F interface and deep inside the F-layer has also interested the researchers [14,15]. The later has been investigated by techniques such as neutron reflectometry and XMCD [14,15].…”

“…Besides, the T C modulation of the S-layer in the presence of F-layer, the contrasting magnetic nature of S/F interface and deep inside the F-layer has also interested the researchers [14,15]. The later has been investigated by techniques such as neutron reflectometry and XMCD [14,15].…”