AVS 53rd International Symposium
    Magnetic Interfaces and Nanostructures Tuesday Sessions
       Session MI-TuM

Invited Paper MI-TuM10
Fingerprinting Magnetization Reversal in Magnetic Nanostructures

Tuesday, November 14, 2006, 11:00 am, Room 2006

Session: Magnetic Nanostructures, Nanoparticles and Interfaces
Presenter: K. Liu, UC Davis
Authors: K. Liu, UC Davis
J.E. Davies, UC Davis
R.K. Dumas, UC Davis
G.T. Zimanyi, UC Davis
O. Hellwig, Hitachi Global Storage Tech.
E.E. Fullerton, Hitachi Global Storage Tech.
J.S. Jiang, Argonne National Lab
S.D. Bader, Argonne National Lab
G. Denbeaux, Univ. at Albany
J.B. Kortright, Lawrence Berkeley National Lab
C.-P. Li, UC San Diego
I.V. Roshchin, UC San Diego
I.K. Schuller, UC San Diego
Correspondent: Click to Email
Magnetization reversal is often complex, yet critical for the understanding and applications of magnetic nanostructures. Here we present recent studies using a first order reversal curve (FORC) method@footnote 1-4@ on a few technologically important systems. In Co/Pt multilayers,@footnote 2@ we have found three distinct stages for reversal domain nucleation, propagation, and annihilation. Interestingly, significant irreversible switching persists for applied fields well beyond the apparent saturation field due to residual bubble domains. In exchange spring magnets,@footnote 3@ we have investigated the effect of the hard layer crystallinity on irreversible switching. In Fe/epitaxial-SmCo films, the reversal proceeds by a reversible rotation of the Fe soft layer, followed by an irreversible switching of the SmCo hard layer. In FeNi/polycrystalline-FePt films, the FeNi and FePt layers reverse in a continuous process via a vertical spiral. The successive vs. continuous rotation of the soft/hard layer system is primarily due to the different hard layer anisotropy. In arrays of Fe nanodots,@footnote 5@, we have studied a vortex state to single-domain transition as the dot size decreases. Striking differences in the FORC diagrams have been observed. The 52nm dots exhibit single domain behavior, whereas the 58 and 67nm dots exhibit vortex states. The FORC method gives quantitative measures of the magnetic phase fractions and vortex nucleation and annihilation fields. These results demonstrate that FORC is a powerful method for magnetization reversal studies, due to its capability of capturing distributions of magnetic properties, sensitivity to irreversible switching, and the quantitative phase information it can extract. @FootnoteText@ *Supported by NSF, ACS-PRF, DOE, UC-CLE, and Sloan Foundation. @footnote 1@Pike, et al, JAP, 85, 6660 (1999). @footnote 2@Davies, et al, PRB 70, 224434 (2004). @footnote 3@Davies, et al, APL 86, 262503 (2005). @footnote 4@Davies, et al, PRB 72, 134419 (2005). @footnote 5@Liu, et al, APL 81, 4434 (2002).