Nanonetworks are model systems of complex nanoparticle assemblies that enable quantitative investigations of the structure-function relationships. Hence, tuning their geometry is often used to optimize specific features needed for the application of the material. For example, different requirements for the hysteresis loop properties are imposed for applications of magnetic nano-assemblies. Theoretically, a complex structure of nanonetworks can support higher-order interactions that, on the other hand, lead to new nonlinear dynamics phenomena and emergent behaviours of the assembly.
We present recent work [1,2,3] on the field-driven spin dynamics at the hysteresis loop of complex nano-assemblies, whose structure is modelled [4] by aggregation of simplexes as preformatted groups of nodes. For the spin dynamics, the interactions embedded on simplexes of different orders occur between Ising spins associated with the network’s nodes. We will demonstrate the impact of the two leading terms, i.e., the antiferromagnetic pairwise couplings, providing the geometric frustrations of the spins on triangles and the 3-spin interactions based on the triangle faces of simplexes. By slowly increasing the external magnetic field from a significant negative to a positive value and back to complete the hysteresis loop, we show how the shape of the loop changes with the competition of these interactions and the structure of the assembly. Moreover, the Barkhausen noise signal that accompanies the slips of the domain walls following the field change exhibits multi-fractal properties. We also find that the avalanches of the domain-wall moves possess self-similarity on a broad scale. These features suggest that the collective dynamics of the self-organized critical type occurs at the interplay of complex geometry and driving mode.
References
[1] B. Tadić and R. Melnik, Self-organized critical dynamics as a key to fundamental features of complexity in physical, biological and social systems, Preprint (2021)
[2] B. Tadić and N. Gupte, Hidden geometty and dynamics of complex systems: spin reversal in complex assemblies with pairwise and triangle-based interactions, Europhys. Lett. 132(6), 60008 (2021)
[3] B. Tadić, M. Andjelković, M. Šuvakov, G.J. Rodgers, Magnetization processes in geometrically frustrated spin networks with self-assembled cliques, Entropy 22(3), 336 (2020)
[4] M. Šuvakov, M. Andjelković, B. Tadić, Hiddem geometries in networks arising from cooperative self-assembly, Scientific Reports 8, 1987 (2018)