Suppressed magnetization inLa0.7Ca0.3MnO3∕YBa2Cu3O7−

Abstract

We studied the magnetic properties of La 0.7 Ca 0.3 MnO 3 / YBa 2 Cu 3 O 7−δ superlattices. Magnetometry showed that with increasing YBa 2 Cu 3 O 7−δ layer thickness the saturation magnetization per La 0.7 Ca 0.3 MnO 3 layer decreases. From polarized neutron reflectometry we determined that this magnetization reduction is due to an inhomogenous magnetization depth profile arising from the suppression of magnetization near the La 0.7 Ca 0.3 MnO 3 / YBa 2 Cu 3 O 7−δ interface.Electron energy loss spectroscopy indicates an increased 3d band occupation of the Mn atoms in the La 0.7 Ca 0.3 MnO 3 layers at the interface. Thus, the suppression of ferromagnetic order at the La 0.7 Ca 0.3 MnO 3 / YBa 2 Cu 3 O 7−δ interface is most likely due to charge transfer between the two materials.

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

“…before this problem with the STO substrates had been fully appreciated, additional experiments of YBCO/LCMO SLs on STO substrates were reported that supported either the dead layer model or the inverse proximity effect model. Hoffmann et al reported an enhancement in the Mn 3d occupation next to the interface and concluded that their PNR data support the dead layer model 27 . On the other hand, Chakhalian et al reported x-ray magnetic circular dichroism (XMCD) data which established the presence of a ferromagnetic Cu moment and thus were interpreted in terms of the "inverse proximity effect model" 28 31 .…”

Magnetic properties and atomic structure of La2/3Ca1/3MnO3–YBa2Cu3O7 heterointerfaces

“…While interesting macroscopic properties such as exchange bias [7] and giant magnetoresistance [10] were observed in some of these structures, the presence of microscopic proximity effects is still under intense investigation [3]. Some experiments have yielded evidence of a strongly suppressed ferromagnetic magnetization on the LCMO side of the interface [5,12], whereas others conclude that copper spins on the YBCO side of the interface are polarized by exchange interactions across the interface, partially compensating the ferromagnetic magnetization of LCMO [13]. Interplay between ferromagnetic and superconducting order parameters [1] is unlikely to be responsible for either of these effects, because the microscopic magnetic properties are not noticeably affected by the superconducting transition [15].…”

“…Interplay between ferromagnetic and superconducting order parameters [1] is unlikely to be responsible for either of these effects, because the microscopic magnetic properties are not noticeably affected by the superconducting transition [15]. Rather, charge transfer across the interface [12,14] and an orbital reconstruction due to the formation of a covalent bond across the interface [14] have been invoked as explanations.…”

“…Recent advances in the synthesis of epitaxial transition metal oxide heterostructures offer intriguing perspectives for the practical realization of such interfaces. In particular, high-quality heterostructures of the metallic ferromagnet La 2/3 Ca 1/3 MnO 3 (LCMO) and the high-temperature superconductor YBa 2 Cu 3 O 7 (YBCO) have been prepared by pulsed-laser deposition (PLD) and investigated with a variety of experimental methods [2][3][4][5][6][7][8][9][10][11][12][13][14][15]. While interesting macroscopic properties such as exchange bias [7] and giant magnetoresistance [10] were observed in some of these structures, the presence of microscopic proximity effects is still under intense investigation [3].…”

Tunnel magnetoresistance in La0.7Ca0.3MnO3∕PrBa2Cu3O7∕La0.7Ca0.3MnO3

“…The reduced Curie temperature and enhanced coercivity of the top layer may be related to changes of the electronic structure at the interface caused by strain, to modified chemical bonding, or even to charge transfer as recently reported for cuprate/manganite heterostructures. 14 Interface effects are expected to be more pronounced in the thinner top layer than in the bottom one. The difference in coercive fields ensures antiparallel alignment of the magnetization of bottom and top electrodes over a wide field interval.…”