Apparatus and methods for generating a uniform magnetic field are provided herein. In certain configurations, a magnetic structure includes one or more pairs of magnets positioned within a housing. The magnets of each pair are arranged in parallel and include poles that are reversed in polarity relative to one another. For example, in certain implementations, a first pair of magnets includes a first magnet and a second magnet arranged side by side, with a north pole of the first magnet adjacent a south pole of the second magnet and with a south pole of the first magnet adjacent a north pole of the second magnet. The housing is implemented using a magnetic redirecting material, which can confine magnetic flux and reduce stray magnetic fields. The magnetic structure can be used to generate a magnetic field that is substantially uniform in a region of interest.