We investigate the frequency of thermally excited vortex oscillations in Co-Fe-B magnetic tunnel junction (MTJ) pillars in the presence of defects. Under a variable in-plane magnetic field, a characteristic behavior is observed: the frequency oscillates from a maximum at certain field values to a steep minimum, which tends towards zero frequency. These frequency variations are described qualitatively well by an analytical model based on the Thiele equation taking into account a single Gaussian pinning potential. It is thus possible to calculate the in-plane depinning field for certain pinning potential parameters. For steep potentials, the depinning is hysteretic and jumps between the pinned and unpinned regime occur due to the presence of an energy barrier. A sharp frequency minimum occurs at an applied field, where a large flat region in the energy landscape is present. From the experiments, the pinning potentials are estimated to be between 0.2eV and 0.4eV. We also perform micromagnetic simulations of the vortex oscillations in the presence of a distribution of pinning centers. The simulations confirm the validity of the Thiele-approach showing that the vortex remains sufficiently rigid.

Vortex dynamics in Co-Fe-B magnetic tunnel junctions in presence of defects / Kuepferling, Michaela; Zullino, S.; Sola, Alessandro; Van de Wiele, B.; Durin, Gianfranco; Pasquale, Massimo; Rott, K.; Reiss, G.; Bertotti, Giorgio. - In: JOURNAL OF APPLIED PHYSICS. - ISSN 0021-8979. - 117:(2015). [10.1063/1.4908142]

Vortex dynamics in Co-Fe-B magnetic tunnel junctions in presence of defects

Kuepferling Michaela;Sola Alessandro;Durin Gianfranco;Pasquale Massimo;Bertotti Giorgio
2015

Abstract

We investigate the frequency of thermally excited vortex oscillations in Co-Fe-B magnetic tunnel junction (MTJ) pillars in the presence of defects. Under a variable in-plane magnetic field, a characteristic behavior is observed: the frequency oscillates from a maximum at certain field values to a steep minimum, which tends towards zero frequency. These frequency variations are described qualitatively well by an analytical model based on the Thiele equation taking into account a single Gaussian pinning potential. It is thus possible to calculate the in-plane depinning field for certain pinning potential parameters. For steep potentials, the depinning is hysteretic and jumps between the pinned and unpinned regime occur due to the presence of an energy barrier. A sharp frequency minimum occurs at an applied field, where a large flat region in the energy landscape is present. From the experiments, the pinning potentials are estimated to be between 0.2eV and 0.4eV. We also perform micromagnetic simulations of the vortex oscillations in the presence of a distribution of pinning centers. The simulations confirm the validity of the Thiele-approach showing that the vortex remains sufficiently rigid.
File in questo prodotto:
File Dimensione Formato  
JAP_Kuepferling_vortex_2015_1.4908142.pdf

accesso aperto

Descrizione: This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article may be found at DOI indicated above.
Tipologia: final published article (publisher’s version)
Licenza: Pubblico - Tutti i diritti riservati
Dimensione 1.45 MB
Formato Adobe PDF
1.45 MB Adobe PDF Visualizza/Apri

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11696/30448
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 9
  • ???jsp.display-item.citation.isi??? 8
social impact