For fundamental science, we demonstrate the combination of spin excitation useful for DNP-enhanced NMR by methods of oxide spintronics. The well-stablished optical spin excitation in InP can now be controlled by very simple and efficient planar spintronics structures.
As a benefit for Nanoengineers, we have proven that the native surface oxide in InP commercial wafers is suitable for spin detection in a tunnel junction-like structure. This avoids the conductance mismatch and complicated non-local geometries. Applications can be the parallel monitoring of electronic spin polarization in InP-based DNP-NMR experiments, or a helicity sensor for infrared photons.
Figure Legend: Setup for the electrical detection of electronic spin polarization. Circularly polarized photons excite colinear spins in the InP (001) surface, detected by the voltage change at the tunnel spin filter terminals.
New J. Phys. 17 022004. (2015). Christian Caspers, Dongyoung Yoon, Murari Soundararajan and Jean-Philippe Ansermet.
Laboratoire de Physique des Matériaux Nanostructurés, École Polytechnique Fédérale de Lausanne EPFL, 1015 Lausanne, Switzerland
We demonstrate opto-spintronics using Fe-doped Indium Phosphide (InP). The method is based on optical orientation of InP conduction electron spins which are electrically detected in planar InP/oxide/Ni tunnel spin filters. We separate the optical excitation from electrical detection, avoiding thus additional interactions of photons with the ferromagnet. Interface engineering provides a surface iron accumulation and semiconducting Fe:In2O3 in the oxide tunnel barrier. The spin filtering effect switches to positive or negative asymmetry, depending on the Fe concentration in Fex:InP. With respect to the Fe-like electronic structure of these oxides, we can explain the opposite spin selection mechanisms as interface effects. In the temperature region where the InP mobility peaks, we find a maximum of spin-dependent asymmetry of in semi-insulating Fe:InP (001), and show the electrical spin detection in hyperpolarized InP also at room temperature. Such robust electronic spin detection in an InP nanodevice is planned to complement dynamic nuclear polarization experiments.