Breakup of thin films of micro magnetic drops in perpendicular fields

New modes of striking drop breakup instabilities of a thin film of micro magnetic drops are experimentally observed under a constant perpendicular field. These modes are shown to depend strongly on the initial sizes of drops. Three modes of well-ordered breakup instability patterns are recorded for drop sizes ranging from diameter \textit{d=400$\mu $m} to\textit{ 1,400$\mu $m}. Mode I instability (\textit{d$\mathbin{\lower.3ex\hbox{$\buildrel<\over {\smash{\scriptstyle=}\vphantom{_x}}$}} $400$\mu $m}) shows a fully evolved central droplet associated with numerous incompletely developed droplets in a formation of evenly distributed waves at a separated outer fluid annulus. These waves at the outer annulus are further destabilized and fully evolve into Mode II instability (\textit{500$\mu $m$\mathbin{\lower.3ex\hbox{$\buildrel<\over {\smash{\scriptstyle=}\vphantom{_x}}$}} $d$\mathbin{\lower.3ex\hbox{$\buildrel<\over {\smash{\scriptstyle=}\vphantom{_x}}$}} $1,000$\mu $m)} which forms an additional outer circular array of droplets$.$ A more vigorous Mode III instability with an additional array of droplets in the middle region and smaller secondary droplets in the outer array is observed for a even bigger initial drop size (\textit{1,100$\mu $m$\mathbin{\lower.3ex\hbox{$\buildrel<\over {\smash{\scriptstyle=}\vphantom{_x}}$}} $d$\mathbin{\lower.3ex\hbox{$\buildrel<\over {\smash{\scriptstyle=}\vphantom{_x}}$}} $1,400$\mu $m}). For drop sizes \textit{d$\ge $1,500$\mu $m, }a more complex Mode IV instability is recorded, which shows disorderly arrangements of numerous droplets in the middle region and derivative droplets at the outer array.