Probing vertically graded anisotropy in FePtCu films

Randy K. Dumas, Yeyu Fang, B. J. Kirby, Chaolin Zha, Valentina Bonanni, Josep Nogués, and Johan Åkerman
Phys. Rev. B 84, 054434 – Published 10 August 2011

Abstract

Field-dependent polarized neutron reflectivity (PNR) and magnetometry are employed to study the magnetic properties of compositionally uniform and graded FePtCu films as a function of annealing temperature (TA). The PNR results are able to directly probe the compositional and anisotropy variations through the film thickness. Further details about how the reversal mechanisms evolve are then elucidated by using a first-order reversal curve technique. The reversal of the graded sample annealed at 300 °C occurs by an initial rapid switching of the dominant soft A1 phase toward the surface of the film, followed by the gradual reversal of the residual hard phase components toward the bottom. This indicates that the anisotropy gradient is not well established at this low TA. A fundamentally different mechanism is found after annealing at 400 °C, where the rapid switching of the entire film is preceded by a gradual reversal of the soft layers. This suggests that the anisotropy gradient has become better established through the film thickness. The field-dependent PNR measurements confirm the existence of an anisotropy gradient, where the lower (higher) anisotropy portions are now toward the bottom (top) of the film because of the Cu compositional gradient. However, after annealing at 500 °C, a single rapid reversal is found, indicating the formation of a uniform hard film. In this case, PNR demonstrates a more uniform magnetic depth profile that is consistent with a uniform reference sample, suggesting significant interdiffusion of the Cu is degrading the compositional and induced anisotropy gradient at this elevated TA.

  • Figure
  • Figure
  • Figure
  • Figure
  • Figure
  • Figure
  • Figure
  • Received 7 January 2011

DOI:https://doi.org/10.1103/PhysRevB.84.054434

©2011 American Physical Society

Authors & Affiliations

Randy K. Dumas1,*, Yeyu Fang2, B. J. Kirby3, Chaolin Zha2, Valentina Bonanni2, Josep Nogués2,4, and Johan Åkerman1,2

  • 1Department of Physics, University of Gothenburg, Gothenburg 412 96, Sweden
  • 2Materials Physics, Royal Institute of Technology (KTH), Kista 164 40, Sweden
  • 3Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
  • 4Institució Catalana de Recerca i Estudis Avançats (ICREA) and CIN2 (ICN-CSIC) and Universitat Autònoma de Barcelona, Catalan Institute of Nanotechnology, Campus de la Universitat Autònoma de Barcelona, Bellaterra (Barcelona) 08193, Spain

  • *randydumas@gmail.com

Article Text (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand
Issue

Vol. 84, Iss. 5 — 1 August 2011

Reuse & Permissions
Access Options
Author publication services for translation and copyediting assistance advertisement

Authorization Required


×
×

Images

×

Sign up to receive regular email alerts from Physical Review B

Log In

Cancel
×

Search


Article Lookup

Paste a citation or DOI

Enter a citation
×