Ferromagnetic/superconducting bilayer structure: A model system for spin diffusion length estimation

Abstract

We report detailed studies on ferromagnet-superconductor bilayer structures. Epitaxial bilayer structures of half metal-colossal magnetoresistive La 2/3 Ca 1/3 MnO3 (HM-CMR) and high-Tc superconducting YBa2Cu3O 7−δ (HTSC) are grown on SrTiO3 (100) single-crystalline substrates using pulsed laser deposition. Magnetization M (T) measurements show the coexistence of ferromagnetism and superconductivity in these structures at low temperatures. Using the HM-CMR layer as an electrode for spin polarized electrons, we discuss the role of spin polarized self injection into the HTSC layer. The experimental results are in good agreement with a presented theoretical estimation, where the spin diffusion length ξFM is found to be in the range of ξFM ≈ 10 nm.

Spin diffusion versus proximity effect at ferromagnet/superconductorLa0.7Ca0.3MnO3∕YBa2Cu3OPeña1, Visani2, García‐Barriocanal3 et al. 2006Phys. Rev. B541251View full textAdd to dashboardCite

“…S can be estimated by the relation S ϳ 3.7ប k B T c / E ex ⌬͑T͒, where E ex ϳ30 K is the average on-site spin exchange interaction in YBCO and ⌬͑T͒ = ⌬͑0͒͑1−T / T c ͒ 0.5 is the temperaturedependent gap. Assuming a value of S =10 −13 s, 41 v F =10 7 cm/ s and that the electron mean free path of YBCO is l 0 = 20 nm, l S can be of the order of 14 nm, in agreement with the 10 nm estimated recently by Soltan et al 43 This work also reports on LCMO/YBCO bilayers although focusing on much thicker YBCO layer thickness.…”

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

“…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]. 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].…”

Preparation of a ferromagnetic barrier in YBa2Cu3O7–δ thinner than the coherence length

“…are exposed to a neighboring YBCO layer and their properties are strongly influenced by them, as found in many studies of LCMO/ YBCO hybrids and superlattices. 2,[5][6][7][8][9][10]12 The film orientation and phase purity of every heterostructure were checked by X-ray diffraction (XRD). A 2h scan for the sample displayed in Fig.…”

“…Although recent progress has been made in understanding the interface physics of oxide heterostructures consisting of oxides with antagonistic long range order (e.g., ferromagnetism and superconductivity), [2][3][4][5][6][7][8][9][10][11][12] little is known about the feasibility of fabricating oxide SFS-Josephson junctions. This holds, in particular, for the subsequent exploration of the properties.…”