Frustrated magnetization reversal in Co/Pt multilayers

Joseph E. Davies,¹ O. Hellwig,² E. E. Fullerton,^2,3 M. Winklhofer,⁴ Kai Liu,⁵ and Robert D. Shull¹

¹Metallurgy Division, NIST, Gaithersburg, MD, 20899

²Hitachi Global Storage Technologies, San Jose, CA

³Center for magnetic recording, University of California, San Diego, CA

⁴Department of Geosciences, University of Munich, München, Germany

⁵Physics department, University of California, Davis, CA 95616

Co/Pt multilayers with perpendicular anisotropy have been the focus of intense studies in recent years due to its applications in perpendicular, heat assisted and bit patterned media [1].  Here we have utilized the first order reversal curve (FORC) method [2,3] to investigate the reversal processes in (Co/Pt)_x multilayers with varying number (X) of bilayer repeats.  Interestingly, some of the FORC’s, in essence part of the minor loops, protrude outside of the major loop for samples with X ranging from 10 to 50.  Transmission x-ray microscopy reveals that, along those protruding FORC’s, the domain topography near remanence consists largely of disconnected stripe domains.  In contrast, in the remanent state along the major loop, the contiguous stripe domains occupy much larger regions. The origin of this exotic behavior lies in residual domains that persist at large reversal fields. These unannihilated domains become the nucleation sites for the subsequent reversal and carve out the size of the contiguous stripe domains. The frustration leads to a higher remanence than that along the major loop, and consequently the protruding FORC’s. Work supported in part by the Sloan Foundation, BaCaTec, and CITRIS.

[1] D. Weller, L. Folks, M. Best, E. E. Fullerton, B. D. Terris, G. J. Kusinski, K. N. Krishnan, and G. Thomas, J. Appl. Phys. 89, 7525 (2001).

[2] J. E. Davies, O. Hellwig, E. E. Fullerton, G. Denbeaux, J. B. Kortright and Kai Liu, Phys. Rev. B 70, 224434 (2004).

[3] C. R. Pike, A. Roberts, and K. L. Verosub, J. Appl. Phys. 85, 6660 (1999).

CATEGORY: Materials

Mentors Name: Dr. Robert Shull

Metallurgy Division, MSEL

B-148, Building 223 Mail stop 8552

Tel: x4047

Fax: x4553

Email: joe.davies@nist.gov

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