Thickness controlled proximity effects in C-type antiferromagnet/superconductor heterostructure

Abstract

Modulation of the superconducting state possessing a C-type antiferromagnetic phase in the Nd 0.35 Sr 0.65 MnO 3 /YBa 2 Cu 3 O 7 heterostructure is investigated, with the Nd 0.35 Sr 0.65 MnO 3 thickness (t) varying from 40 to 200 nm. Both the superconducting transition temperature and the upper critical field along the c-axis decrease with increasing t; while the in-plane coherence length increases from 2.0 up to 3.6 nm. Meanwhile, the critical current density exhibits a field-independent behavior, indicating an enhanced flux pinning effect. Furthermore, low-temperature spin canting induces a breakdown and re-entrance of the superconductivity, demonstrating a dynamic completion between the superconducting pairing and the exchange field. An unexpected colossal magnetoresistance is observed below the superconducting re-entrance temperature at t = 200 nm, which is attributed to the dominant influence of the exchange field over the pairing energy.Investigating the proximity effect between different ordered phases provides unique opportunities to study fundamental physics as well as new phenomena for applications [1][2][3][4][5] . The re-discovery of colossal magnetoresistance (CMR) materials 6 and their compatibility with high-temperature superconductors (HTS) 7 to form coherent heterostructures have further intensified the research in the area of the proximity effect [8][9][10][11] . In general, superconductivity is incompatible with ferromagnetism owing to the breaking apart of the Cooper pairs by the exchange field. A recent report has demonstrated the interference effects between a quasiparticle and electron in the conductance across the YBa 2 Cu 3 O 7 (YBCO)/La 0.7 Ca 0.3 MnO 3 interface, which establishes an understanding for the long-range proximity effects between d-wave superconductivity and half-metallic ferromagnetism 12 . In addition, the strength of the exchange interaction may be modulated by modifying the form of the thin film, making this process suitable for tailoring the critical parameters of superconductors for technological applications 13,14 . It is known that Nd 0.35 Sr 0.65 MnO 3 (NSMO) exhibits C-type antiferromagnetism 15,16 below the Néel temperature (T N = 270 K), with spins aligned ferromagnetically along the c-direction but antiferromagnetically coupled within the a-b plane. However, NSMO exhibits a canted ferromagnetic (FM) phase at around 50 K via the action of the mobile electron hopping 17 . Our previous study revealed that the proximity effect of spin canting in NSMO led to a finite resistance and effective flux pinning at the superconducting state of YBCO/NSMO 10 . In general, the proximity effect of the superconducting and antiferromagnetic (AFM) orderings is much less explored because the AFM interaction does not create an internal field significant enough to affect superconductivity. The reason NSMO has considerable effect upon YBCO is that NSMO is not an isotropic antiferromagnet (G-type) but is a C-type antiferromagnet, meaning that the Mn moment aligns parallel along the c-a...

Engineering low-temperature proximity effect in clean metals by spectral singularities

“…The proximity effect in superconductor-normal metal (SN) junctions has been extensively investigated in numerous studies, both experimentally [7,8] and theoretically [9,10]. These investigations have explored the phenomenon in both clean and dirty limits [11,12] at temperatures approaching absolute zero, as well as at finite temperatures [13].…”

Strain effect on orbital and magnetic structures of Mn ions in epitaxial Nd0.35Sr0.65MnO3/SrTiO3 films using X-ray diffraction and absorption

“…Many studies of the composition Nd 0.35 Sr 0.65 MnO 3 (NSMO) (x = 0.65) have focused on the charge transfer at the interface with STO substrate 9 , 18 . The interaction between magnetism and superconductivity in YBa 2 Cu 3 O 7 /NSMO/LaAlO 3 multilayers was investigated early in the development of the field, revealing very interesting FM state that arises from the canted-antiferromagnetism ( c AFM) of Mn ions in the NSMO layers 19 . This phenomenon indicates that the spin moment of Mn ions aligns along the c -axis in one-dimensional orientation and compensates for the neighboring c -axis spin chain with an opposite direction in the lattice structure.…”