J. Dura

Publications (3)7.37 Total impact

• Article: Thickness-dependent coercive mechanisms in exchange-biased bilayers

  C. Leighton, M. R. Fitzsimmons, A. Hoffmann, J. Dura, C. F. Majkrzak, M. S. Lund, Ivan K. Schuller
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  ABSTRACT: We present an investigation of the effect of ferromagnetic layer thickness on the exchange bias and coercivity enhancement in antiferromagnet/ferromagnet bilayers. At low temperatures both the exchange bias and coercivity closely follow an inverse thickness relationship, contrary to several recent theoretical predictions. Furthermore, the temperature dependence of the coercivity as a function of the ferromagnet thickness provides clear evidence for the existence of two distinct regimes. These regimes were probed with conventional magnetometry, anisotropic magnetoresistance, and polarized neutron reflectometry. At low thickness the coercivity exhibits a monotonic temperature dependence, whereas at higher thickness a broad maximum occurs in the vicinity of the Néel temperature. These regimes are delineated by a particular ratio of the ferromagnet to antiferromagnet thickness. We propose that the ratio of the anisotropy energies in the two layers determines whether the coercivity is dominated by the ferromagnetic layer itself or the interaction of the ferromagnetic layer with the antiferromagnet.
  Phys. Rev. B. 01/2002; 65(6).
• Article: Two-stage magnetization reversal in exchange biased bilayers.

  C Leighton, M R Fitzsimmons, P Yashar, A Hoffmann, J Nogués, J Dura, C F Majkrzak, I K Schuller
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  ABSTRACT: MnF(2)/Fe bilayers exhibit asymmetric magnetization reversal that occurs by coherent rotation on one side of the loop and by nucleation and propagation of domain walls on the other side of the loop. Here, we show by polarized neutron reflectometry, magnetization, and magnetotransport measurements that for samples with good crystalline "quality" the rotation is a two-stage process, due to coherent rotation to a stable state perpendicular to the cooling field direction. The result is remarkably asymmetrically shaped hysteresis loops.
  Physical Review Letters 06/2001; 86(19):4394-7. · 7.37 Impact Factor
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  Available from: psu.edu

  Article: The magnetic structure of Cr in exchange coupled Fe/Cr(001) superlattices

  A. Schreyer, C. F. Majkrzak, T. Schmitte, P. Bodeker, A. Abromeit, J. Dura, T. Watanabe
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  ABSTRACT: Using polarized neutron reflectometry (PNR) and high angle neutron scattering from Fe/Cr(001) superlattices, we demonstrate how the non-collinear exchange coupling between the Fe layers is caused by a frustration between antiferromagnetic Cr domains. This induces a spiral modulation of the Cr not observed in bulk. PNR and magnetization measurements show that the noncollinear coupling vanishes above the Neel temperature of this commensurate Cr order. The results are consistent with a recent model for non-collinear exchange coupling over antiferromagnetic interlayers. Typeset using REVT E X 1 The oscillatory exchange coupling between ferromagnetic (FM) layers over a non-FM interlayer [1], the related giant magnetoresistance e#ect [2] and the biquadratic or noncollinear (NC) exchange coupling between FM layers [3,4] were important recent discoveries in the field of thin film magnetism [5]. Fe/Cr(001) layered structures played the key role in these findings. Since Cr is antiferr...
  02/1970;