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Tuesday, April 28, 2015
3:30 PM - 4:30 PM
CNLS Conference Room (TA-3, Bldg 1690)

Q-Mat Seminar

Artificial Spin Ice: From Scientific Toy to Material by Design

Cristiano Nisoli

Frustration, the presence of constraints/interactions that cannot be completely satisfied, is ubiquitous in the physical sciences as well as in life and a source of degeneracy and disorder. This in turn gives rise to new and interesting physical phenomena. In the past seven years a new perspective has opened in the study of frustration through the creation of artificial frustrated magnetic systems [1,2]. These materials consist of arrays of lithographically fabricated single-domain ferromagnetic nanostructures that behave like giant Ising spins. The nanostructures’ interactions can be controlled through appropriate choices of their geometric properties and arrangement on a (frustrated) lattice. The degrees of freedom of the material can not only be directly tuned, but also individually observed. Experimental studies have unearthed intriguing connections to the out-of-equilibrium physics of disordered systems and nonthermal "granular" materials, while revealing strong analogies to spin ice materials and their fractionalized magnetic monopole excitations, lending the enterprise a distinctly interdisciplinary flavor [2-7]. The experimental results have also been closely coupled to theoretical and computational analyses, facilitated by connections to classic models of frustrated magnetism, whose hitherto unobserved aspects have here found an experimental realization.

In this talk we review considerable experimental and theoretical progress in this field. We outline the more recent developments and future vistas for progress in this rapidly expanding field. We then show how recent results have opened paths to new territories. Higher control, inclusive of genuine thermal ensembles [8,9] have replaced the earlier and coarser methods based on magnetic agitation [2,6]. Dynamical versions are now being realized [9,10], characterized in real time via PEEM, revealing statistical mechanics in action. This has lead us to afford implementation of new geometries [11,12], not found in nature, for dedicated bottom up design of desired emergent properties [13]. Born as a scientific toy to investigate frustration-by-design, artificial spin ice might now be used to open “a path into an uncharted territory, a landscape of advanced functional materials in which topological effects on physical properties can be explored and harnessed. [14]

[1] R. F. Wang et al., Nature 439, 303-306 (2006); [2] C. Nisoli et al., Rev. Mod. Phys. 85 (4), 1473 (2013); [3] S. Ladak, et al, Nature Physics 6, 359 (2010); [4] P. E. Lammert, et al, Nature Physics 6, 786-789 (2010); [5] E. Mengotti et al. Nature Physics, 7 68 (2011); [6] C. Nisoli et al. Phys. Rev. Lett. 105, 047205 (2010); [7] W. R. Branford et al. Science 335 1597 (2012); [8] Z. Sheng et al. Nature 500 (7464), 553 (2013). ; [9] A. Farhan et al. Nature Physics 9, 375–382(2013); [10] V. Kalpaklis et al. Nature Nanotechnology 9, 514 (2014); [11] M. Morrison et al. New Journal of Physics 15 (4), 045009 (2013); [12] G-W Chern et al Phys. Rev. Lett. 111 (17), 177201 (2013); [13] Ian gilbert et al., Nature Physics, 10 (9), 670-675 (2014); [14] R. L. Stamps, News and Views, Nature Physics, doi:10.1038/nphys3072 (2014)

Host: Tammie Nelson