  Anisotropic magnetoresistance and negative magnetoresistance for in-plane
fields are compared for the LaAlO3 /SrTiO3 interface and the symmetric Nb-doped
SrTiO3 heterostructure. Both effects are exceptionally strong in LaAlO3 /SrTiO3
. We analyze their temperature, magnetic field and gate voltage dependencies
and find them to arise from a Rashba type spin-orbit coupling with magnetic
scatterers that have two contributions to their potential: spin exchange and
Coulomb interaction. Atomic spin-orbit coupling is sufficient to explain the
small effects observed in Nb-doped SrTiO3 . These results clarify contradicting
transport interpretations in SrTiO3 -based heterostructures.
