Infinite magneto-resistance and bipolar effect in spin valves driven by spin batteries

It is shown that spin valves under suitable symmetry conditions exhibit an ON-OFF response to a spin battery. While a spin valve driven by a charge battery displays the usual GMR (Giant Magneto-Resistance), a pure spin current or pure spin accumulation can generate an infinite magneto-resistance effect(IMR). In practice the effect is curtailed by asymmetry but the achievable magneto-resistance ratio is still predicted to be unusually large in several example setups. It is closely related to the bipolar effect (BE) of Johnson transistor which can be triggered under the same symmetry conditions.