An apparatus for providing a magnetic field includes a magnet having a surface, and a structure disposed above the magnet surface. The structure includes a material of high magnetic permeability. The apparatus provides an interface between the material of high magnetic permeability and a material of low magnetic permeability. The apparatus may have two poles in magnetic communication with the magnet, the poles extending above the surface of the magnet, and the structure is disposed between the poles. The structure may have alternating regions of high magnetic permeability and low magnetic permeability. The apparatus alters the magnetic field of the magnet to reduce or remove a disorder in the magnetic field, and/or decrease the magnitude of the magnetic field, and/or induce a distortion in the magnetic field, and/or align or re-align the magnetic field, and/or orientate or re-orientate the magnetic field, and/or alter distribution or shape of the magnetic field.