In this talk, we give localise the spectrum of a discrete
magnetic Laplacian on a finite graph using techniques similar to the
Dirichlet-Neumann-bracketing for continuous problems. As application we
localise the spectrum of periodic Laplacians using the fact that the
fibre operators from Floquet Bloch theory can be seen as magnetic
Laplacians. Finally, we use the bracketing ideas to order spectra of
different graphs, and show how certain graph manipulations change the
spectrum.