In this paper we perform nanofabrication of square artificial spin ices with different lattice parameters, in order to investigate the roles of vertex excitation on the features of the system. In particular, the character of magnetic charge distribution asymmetry on the vertices are observed under magnetic hysteresis loop experiments. We then compare our results with simulation using an emergent Hamiltonian containing objects such as magnetic monopoles and dipoles in the vertices of the array (instead of the usual Hamiltonian based on the dipolar interactions among the magnetic nanoislands). All possible interactions between these objects are considered (monopole-monopole, monopole-dipole and dipole-dipole). Using realistic parameters we observe very good match between experiments and theory, which allow us to better understand the system dynamics in function of monopole charge intensity.

Sets of nanomagnets are often utilized to mimic cellular automata in design of nanomagnetic logic devices or frustration and emergence of magnetic charges in artificial spin ice systems. in previous work we showed that unidirectional arrangement of nanomagnets can behave as artificial spin ice, with frustration arising from second neighbor dipolar interaction, and present good magnetic charge mobility due to the low string tension among charges. Here, we present an experimental investigation of magnetic charge population and mobility in function of lateral and longitudinal distance among nanomagnets. Our results corroborate partially the theoretical predictions, performed elsewhere by emergent interaction model, could be useful in nanomagnet logic devices design and brings new insights about the best design for magnetic charge ballistic transport under low external magnetic field with magnetic charge mobility tunning for application in magnetricity.

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In this work, we present screening of magnetic monopole and dipole by the presence of a 20 nm aluminum cover layer on square artificial spin ice systems. Our measurements were performed by magnetic force microscopy on samples with and without aluminum at remanence, after application of successive external magnetic field steps. Experimental results show that both evolution of magnetization and monopole population under external field are affected by the aluminum presence. Very good agreement between those results and excitation model simulations was found when both emergent magnetic monopole and dipole strengths decrease on the presence of the aluminum cap. We suggest that the observed strength weakening of emergent particles occurs due to its field screening by aluminum-free electrons. The screening on the presented heterostructure could be used for devices design with different magnetic monopole mobility or for selective thermodynamic activation in samples close to superparamagnetic regime.

In this work we present emergent screening of magnetic monopole and dipole by the presence of 20nm aluminum cover layer onsquare artificial spin ice (ASI) systems. Our results were obtained in base of magnetic atomic force measurements, performedafter external magnetic field steps application. We show that the evolution of magnetization and monopole population is affectedby the aluminum presence and attribute that phenomena to the proximity effect, which is responsible for the magnetizationvanish of the first atomic layers at the ferromagnetic interface. Using experimental values to estimate the decrease in thenanomagnetic dipole value used in an emergent excitation model and in the switching field distribution heterogeneity usedin simulations, we observe a very good agreement among experimental and simulation results. The presented emergentscreening could be used in new ASI geometries for thermodynamic activation or proposition of devices with selective magneticmonopole mobility.