Tuning Magnetic Anisotropy in Nanostructures for Biomedical and Electromagnetic Applications

Magnetic nanoparticles have been building blocks in applications ranging from high density recording to spintronics and nanomedicine [1]. Magnetic anisotropies in nanoparticles arising from surfaces, shapes, and interfaces in hybrid structures are important in determining the functional response in various applications. In this talk I will first introduce the basic aspects of anisotropy and discuss resonant radio-frequency (RF) transverse susceptibility, which we have used extensively, as a powerful method to probe the effective anisotropy in magnetic materials. The tuning of anisotropy has a direct impact on the performance of functional magnetic nanoparticles in biomedical applications such as contrast enhancement in magnetic resonance imaging and magnetic hyperthermia for cancer therapy. I will focus on the role of tuning surface and interfacial anisotropy with a goal to enhance specific absorption rate or heating efficiency. Strategies going beyond simple spherical structures to include exchange coupled core-shell nanoparticles, nanowires, and nanotubes, can be exploited to increase heating efficiency in magnetic hyperthermia [2], [3]. In addition to biomedical applications, composites of anisotropic nanoparticles dispersed in polymers pave the way to a range of electrically and magnetically tunable materials for RF and microwave device applications [4]. This lecture will combine insights into fundamental physics of magnetic nanostructures along with recent research advances in their application to nanomedicine and electromagnetic devices. [1] E. A. Périgo, G. Hemery, O. Sandre, D. Ortega, E. Garaio, F. Plazaola, and F. J. Teran, “Fundamentals and advances in magnetic hyperthermia,” Appl. Phys. Rev., vol. 2, 041302, 2015.
[2] Z. Nemati, J. Alonso, H. Khurshid, M. H. Phan, and H. Srikanth, “Core/shell iron/iron oxide nanoparticles: Are they promising for magnetic hyperthermia?” RSC Advances, vol. 6, 38697, 2016.
[3] H. Khurshid, M.-H. Phan, P. Mukherjee, and H. Srikanth, “Tuning exchange bias in Fe/-Fe2O3 core-shell nanoparticles: Impacts of interface and surface spins,” Appl. Phys. Lett., vol. 104, 072407, 2014.
[4] K. Stojak, S. Pal, H. Srikanth, C. Morales, J. Dewdney, T. Weller, and J. Wang, “Polymer nanocomposites exhibiting magnetically tunable microwave properties,” Nanotechnology, vol. 22, 135602, 2011.