  Heusler alloys based magnetic tunnel junctions can potentially provide high
magnetoresistance, small damping and fast switching. Here junctions with
Co2FeAl as a ferromagnetic electrode are fabricated by room temperature
sputtering on Si/SiO2 substrates. The doping of Boron in Co2FeAl is found to
have a large positive impact on the structural, magnetic and transport
properties of the junctions, with a reduced interfacial roughness and
substantial improved tunneling magnetoresistance. A two-level magnetoresistance
is also observed in samples annealed at low temperature, which is believed to
be related to the memristive effect of the tunnel barrier with impurities.
