Magnetic circuit using negative magnetic susceptibility

A fuel injector for an internal combustion engine, comprising:

• a body having a passage extending along a longitudinal axis between inlet and outlet ends;
• a stator member;
• an armature member being movable with respect to the stator member between a first. configuration and a second configuration, the armature member including a closure member proximate the outlet end and contiguous to a seat in the first configuration, and spaced from the seat in the second configuration;
• an electromagnetic coil surrounding the passage, the coil disposed in a housing and being energizable to provide magnetic flux that moves the armature between the first and second configuration to permit fuel flow through the passage between the inlet and outlet ends;
• and
• a diamagnetic member proximate the electromagnetic coil so that when the electromagnetic coil is energized the diamagnetic member focuses the magnetic flux to reduce magnetic flux leakage between the stator and the electromagnetic coil;
• wherein the electromagnetic coil includes a hollow core, the diamagnetic member includes a wall defining a hollow cylinder, the wall having an inner surface and an outer surface, the diamagnetic member being disposed at least partially in the hollow core;
• and
• wherein the coil housing surrounds the coil, the inner surface of the wall confronts a portion of the stator, and the outer surface of the wall confronts a portion of the coil.