Experiments with 2D quasistatic and shaken arrays of permanent magnet N-mers ($N \geq 1$)

We extend methods used to study macroscopic grains (contact forces) to 2D ($x,y$) arrays of N-mers of cylindrical (L=D=3.18 mm) Nd-Fe-B magnets in a rectangular cell with glass plates $\Delta z \sim $3.3 mm apart and parallel to magnet faces. Aligned monomers repel with a measured $d^{-4}$ (dipole-dipole) force dependence, with $d$ the separation between cylinder axes. With fixed, aligned monomers separated by 6.35 mm along the cell walls, hundreds of aligned monomers can move in the cell subject to magnet-glass friction and gravity (either $\parallel $ or $\perp $ to $z$) but without contacting each other or the walls. Quasistatically moving one wall to decrease volume $V$ increases pressure $P$ on the magnetic particles and leads to ordering observed with annealing. Driving the array, e.g., by shaking one wall, can produce disorder; we study how this varies with driving strength at fixed $V$ or $P$. Replacing all non-wall monomers with similarly aligned tetramers (3 magnets magnetically bound to an inverted magnet) allows for more ordered states in quasistatic experiments; macroscopic, internal degrees of freedom into which energy can flow in driven experiments; and rearrangements (``chemical reactions") for strong driving.