Coils for large standoff relaxometry with unilateral magnets

•Surface loop coils typically used in single-sided (unilateral) NMR suffer from significant eddy current shielding in the presence of conductive blocks of magnetic material used to generate the static field, B0.•The fringe coil probe geometry harnesses eddy currents to achieve superior signal to noise.•The narrow vertical profile of the fringe coil geometry makes full use of the magnet standoff distance and maximizes sample penetration.•The opposed split fringe coil, a variant of the fringe coil, can be adjusted to match the standoff distance of the magnet, further improving signal to noise.