In our new paper published in New Journal of Physics , we present the physics of assemblies composed of magnetized spheres. Although magnetic assemblies possess some features of magnetic colloids and particles, they remain athermal systems.
Contrary to the apparent simplicity of such systems, we show that elaborated physical behaviors can be obtained like the existence of metastable states.
From simple processes, non-trivial configurations are built, keeping the memory of magnetic frustration. We nicknamed them “ghost junctions“. Surprisingly, those magnetic pseudoparticles behave like magnetic monopoles. Coulomb-like interactions are indeed obtained. The fact that our findings are reminiscent of recent discoveries in spin ice systems  is puzzling because we work at a much larger scale.
Moreover, everyone can build his own monopole for a few dollars ! The movie here below explain how to proceed.
 N.Vandewalle and S.Dorbolo, New J. Phys. 16, 013050 (2014) – open access
 C.Castelnovo, R.Moessner and S.L.Sondhi, Nature 451, 42 (2008)