Effects of ferromagnetic nanopillars on spin coherence in an InGaAs quantum well

•An array of soft-magnetic CoFe pillars was patterned on an InGaAs quantum well.•The CoFe pillars affect electron spin coherence in the quantum well.•Electron spin coherence was deduced from comparative antilocalization experiments.•The array induces spin scattering analogous to spin–orbit interaction.

Low-temperature antilocalization measurements are used to investigate the interactions between a two-dimensional electron system in an In0.53Ga0.47As quantum well in an InGaAs/InAlAs heterostructure, and the magnetic moments of CoFe nanopillars located on the heterostructure surface. With CoFe nanopillars, a decrease in spin coherence time is observed, attributed to the spatially varying magnetic field from the local moments. A good agreement between the data and calculations suggests that the CoFe nanopillars also generate an appreciable average magnetic field normal to the surface of value ~35 G at the quantum well. The measurements further show that surface metal coverage increases mobility, and for non-magnetic coverage increases spin coherence time, consistent with the Elliott–Yafet spin-decoherence mechanism. Phase coherence times decrease as the temperature decreases, consistent with phase decoherence via the Nyquist mechanism.