Space-Charge Induced Pauli Blockade Effect in Tunnel Junctions with Half-Metallic Electrodes*

A space-charge induced Pauli spin blockade effect has been observed in the magnetic tunnel junction consisting of La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ (LSMO) electrodes and SrTiO$_{3}$ barrier at temperatures up to 100 K. The blockade voltage under zero magnetic field provides a direct measurement of the energy gap between the Fermi energy and the top of the minority spin valence band of the LSMO. Outside the spin blockade regime, the low temperature conductance oscillates with the bias voltage as the trap centers are charged by electrons. The spin blockade can be lifted when the trap levels are thermally activated or when a large magnetic field lowers the LSMO minority spin mobility edge to below the Fermi energy. A very large magnetoresistance up to 10000{\%} is observed and is correlated to the blockade effect. $^{\ast }$Email: apli@ornl.gov