Traversing the Minor-Loop Landscape with the FORC Technique

Dustin Gilbert (Physics Department, University of California, Davis)

Probing the microscopic magnetic characteristics in realistic, non-uniform materials and interacting systems has been a long-standing challenge, crucial both for fundamental science and technological applications. The first order reversal curve (FORC) technique has proven itself as an engine to interpret the minor loop landscape and extract these details. In this talk, I will discuss a few recent examples of our FORC studies on nanomagnets. In pseudo-spin-valves of (Co/Pd)/Cu/(Co/Ni) with perpendicular anisotropy, we have found a novel crossover between vertically and laterally correlated magnetization reversal modes which can be manipulated by both temperature variation and cycling of the magnetic field. The contrasting magnetic configurations offer a new handle to tune spin disorders and giant magnetoresistance (GMR) effects [1]. In single layer and exchange coupled composite granular recording media, variations of physical characteristics can be conveniently captured by FORC analysis, which significantly speeds up the media characterization [2]. In patterned arrays of elliptical nanomagnets, the tunable dipolar interaction manifest in the FORC diagram, both qualitatively and quantitatively. Using a physical picture we construct the interacting FORC distribution from the non-interacting case, reproducing all the experimentally observed features. From this we determine the origin of the FORC features and quantitatively determine the interaction field strength, which agrees well with calculated values [3]. Time permitting I will discuss our current study on high anisotropy L10 FeCuPt alloys [4].

*Work supported by the NSF (ECCS-0725902, ECCS-0925626, DMR-1008791, ECCS-1232275).

[1]. J. E. Davies, D. A. Gilbert, M. Mohseni, R. K. Dumas, J. Akerman and Kai Liu, Appl. Phys. Lett., 103, 022409 (2013). [2]. B.F. Valcu, D.A. Gilbert, and Kai Liu, IEEE Trans. Magn., 47, 2988, (2011). [3]. D. A. Gilbert, G. T. Zimanyi, R. K. Dumas, M. Winklhofer, A. Gomez, N. Eibagi, J. L. Vicent, and Kai Liu, Scientific Reports, to appear; arXiv:1401.7749. [4]. D. A. Gilbert, L. W. Wang, T. J. Klemmer, J. U. Thiele, C. H. Lai, and Kai Liu, Appl. Phys. Lett., 102, 132406, (2013).

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