Ferromagnetic transition in EuS-PbS multilayers

Abstract

Document VersionPublisher's PDF, also known as Version of Record (includes final page, issue and volume numbers)Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication Citation for published version (APA):Stachow-Wojcik, A., Story, T., Dobrowolski, W., Arciszewska, M., Galazka, R. R., Kreijveld, M. W., ... Sipatov, A. Y. (1999). Ferromagnetic transition in EuS-PbS multilayers. Physical Review B, 60(22), 15220-15229. DOI: 10.1103/PhysRevB.60.15220 General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. The magnetic properties of multilayers of ferromagnetic EuS intercalated with diamagnetic PbS were studied as a function of the EuS layer thickness ͑varying from 2 to 200 ML͒. The critical temperature T C of the paramagnet-ferromagnet phase transition was determined from magnetization vs temperature measurements and was found to depend on the underlying substrate ͓KCl ͑100͒ vs BaF 2 ͑111͔͒ as well as on the thickness of the EuS layer. For thick layers (d EuS Ϸ200 ML), which mimic semibulk EuS, the T C values were found shifted with respect to the bulk EuS ͑about 1 K up for layers grown on KCl and about 3 K down for layers grown on BaF 2 ). This effect is attributed to stress resulting mainly from the difference of thermal expansion coefficients between the substrate and the structure. For thin layers (d EuS Ͻ10 ML), a systematic reduction of T C with decreasing EuS layer thickness was observed. This behavior is discussed from two points of view: ͑a͒ the reduction of the average number of magnetic neighbors because of the increasing role of the interface for the thin layers, and ͑b͒ the three-dimensional/two-dimensional ͑3D/2D͒ crossover from a 3D Heisenberg-type ferromagnet to a 2D XY or Ising-like sy...

Semiconductor Ferromagnetic Structures

“…EuS and PbS crystallize in the same cubic (rock salt) crystal structure and the lattice mismatch between these two crystals is only 0.5%. Since PbS is a typical diamagnet, magnetically the EuS-PbS multilayers are all-semiconducting ferromagnet-diamagnet nanostructures [23]. EuS-PbS multilayers form PbS multiple quantum wells with fundamental electronic transitions in the infrared [24,25].…”

“…For EuS, the magnetic interactions are important only for nearest (z1 ) and next nearest (z2 ) magnetic neighbors. Since the number of magnetic neighbors varies for ions located in different layers, the average number of neighbors depends on the number n of EuS monolayers in the layer, as well as on the growth direction, and on the intermixing profile at the interface [23]. The final expression for the Curie temperature is TC( n) = TC ( b )…”

“…w h e r e c is a numerical parameter [23]. The application of other concepts (finite size scaling or exact calculations for the Ising systems) to the analysis of the thickness dependence of the Curie temperature in EuS-PbS multilayers is discussed in [23].…”

“…The application of other concepts (finite size scaling or exact calculations for the Ising systems) to the analysis of the thickness dependence of the Curie temperature in EuS-PbS multilayers is discussed in [23]. The Curie temperatures TC of EuS-PbS multilayers are shifted with respect to the Curie temperature of bulk EuS crystal TC ( b), with the shift ΔTC = Tc -TC(b) depending on the substrate.…”

“…We attribute this shift of ferromagnetic critical temperature to the in-plane biaxial stress present in EuS-PbS structures. This stress changes the interspin distances and the exchange integrals Ji, eventually changing the ferromagnetic transition temperature [23]. An analysis shows that the most important source of stress in EuS-PbS multilayers is the thermal stress due to the difference between the thermal expansion coefficients (TEC) of the substrate and the multilayer.…”