Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Controlling the strength of ferromagnetic order in YBa2Cu3O7/La2/3Ca1/3MnO3 multilayers
Stockholm University, Faculty of Science, Department of Physics. University of Fribourg, Switzerland.
Show others and affiliations
2019 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 100, no 11, article id 115129Article in journal (Refereed) Published
Abstract [en]

With dc magnetization and polarized neutron reflectometry we studied the ferromagnetic response of YBa2Cu3O7/La2/3Ca1/3MnO3 (YBCO/LCMO) multilayers that are grown with pulsed laser deposition. We found that whereas for certain growth conditions (denoted as A type) the ferromagnetic moment of the LCMO layer is strongly dependent on the structural details of the YBCO layer on which it is deposited, for others (B type) the ferromagnetism of LCMO is much more robust. Both kinds of multilayers are of similar structural quality, but electron energy-loss spectroscopy studies with a scanning transmission electron microscope reveal an enhanced average Mn oxidation state of +3.5 for the A-type as opposed to the B-type samples, for which it is close to the nominal value of +3.33. The related, additional hole doping of the A-type LCMO layers, which likely originates from La and/or Mn vacancies, can explain their fragile ferromagnetic order, since it places them close to the boundary of the ferromagnetic order at which even weak perturbations can induce an antiferromagnetic or glassy state. On the other hand, we show that the B-type samples allow one to obtain YBCO/LCMO heterostructures with very thick YBCO layers and, yet, strongly ferromagnetic LCMO layers.

Place, publisher, year, edition, pages
2019. Vol. 100, no 11, article id 115129
National Category
Condensed Matter Physics
Research subject
Physics
Identifiers
URN: urn:nbn:se:su:diva-172857DOI: 10.1103/PhysRevB.100.115129ISI: 000486636200001OAI: oai:DiVA.org:su-172857DiVA, id: diva2:1350262
Available from: 2019-09-11 Created: 2019-09-11 Last updated: 2019-10-14Bibliographically approved
In thesis
1. Pulsed laser deposition and nanofabrication of mesoscopic devices based on cuprates and manganites
Open this publication in new window or tab >>Pulsed laser deposition and nanofabrication of mesoscopic devices based on cuprates and manganites
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis explores the growth, the nano-fabrication and the study of the magneto-transport properties of Superconductor/Ferromagnet/Superconductor (SFS) structures from complex oxides such as the high Tc superconducting cuprate YBa2Cu3O7 (YBCO) and the ferromagnetic manganites La2/3Ca1/3MnO3 and La2/3Sr1/3MnO3 (LCMO and LSMO), deposited with the pulsed laser deposition (PLD) technique.The present work has been possible thanks to the collaboration between the “Magnetism and Superconductivity” Group at the University of Fribourg, in Switzerland, and the “Experimentell Kondenserade Materiens Fysik” Group at Stockholm University, in Sweden.

Earlier, the two research groups in Fribourg and Stockholm had studied SFS structures from YBCO/LaMnO3/YBCO multilayers with 20 nm thick ferromagnetic and insulating LaMnO3 barriers, and obtained signs of an unconventional spin-triplet current across these structures. This finding motivated the present thesis work with a focus on two main aspects.

Firstly, to explore other candidate materials suitable as barriers and optimise their growth conditions as to maintain a large ferromagnetic moment and thus a high spin polarisation of the charge carriers. Secondly, to study what happens when the thickness of the ferromagnetic and insulating LaMnO3 barrier is reduced well below 20 nm to enable larger supercurrents.

It has been shown for a series of YBCO/LCMO multilayers that the ferromagnetic moment of LCMO depends critically on the PLD growth conditions as well as on the thickness and even structural details of the YBCO layer on which they are grown. Furthermore, a protocol has been established to grow heterostructures with strongly ferromagnetic manganite layers embedded in thick YBCO layers by optimising the PLD growth conditions and by substituting the bottom YBCO layer with a Co and Ca substituted version of YBCO that has a tetragonal structure (tYBCO) instead of the orthorhombic one of plain YBCO.

Devices suitable for perpendicular magneto-transport measurements have been nano-fabricated from YBCO/manganite/YBCO multilayers with ~10 nm thick LCMO and LSMO layers as the F barriers. While no clear indications of a spin-triplet component of the superconducting order parameter have been obtained yet, a negative and hysteretic magneto-resistance has been observed that is indicative of a strong ferromagnetic order in the thin manganite barrier. The latter suggests a potential memory functionality of such structures that could be exploited in future spintronic memory devices.

Moreover, devices have been fabricated on SFS structures with a reduced thickness of the LaMnO3 barrier of 10 nm and 5 nm. These samples were grown prior to the beginning of this PhD work using non optimised growth conditions, and it was found that the ferromagnetic properties of these LaMnO3 barriers are strongly deteriorated. It remains to be seen whether the ferromagnetic order of such thin LaMnO3 layers can be also recovered by using the optimised growth conditions as for LSMO and LCMO.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2019. p. 109
Keywords
cuprates, manganites, pulsed laser deposition, nano-fabrication, heterostructures
National Category
Condensed Matter Physics
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-172861 (URN)978-91-7797-833-6 (ISBN)978-91-7797-834-3 (ISBN)
Public defence
2019-10-28, FP41, hus 1, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Submitted.

Available from: 2019-10-03 Created: 2019-09-11 Last updated: 2019-09-24Bibliographically approved

Open Access in DiVA

No full text in DiVA

Other links

Publisher's full text

Search in DiVA

By author/editor
de Andrés Prada, Roberto
By organisation
Department of Physics
In the same journal
Physical Review B
Condensed Matter Physics

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 26 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf