Coherent manipulation of nuclear spins using spin injection from a half-metallic spin source

We have developed a nuclear magnetic resonance (NMR) system that uses spin injection from a highly polarized spin source. Efficient spin injection into GaAs from a half-metallic spin source of Mn-rich Co2MnSi enabled an efficient dynamic nuclear polarization of Ga and As nuclei in GaAs and a sensitive detection of NMR signals. Moreover, coherent control of nuclear spins, or the Rabi oscillation between two quantum levels formed at Ga nuclei, induced by a pulsed NMR has been demonstrated at a relatively low magnetic field of similar to 0.1 T. This provides a novel all-electrical solid-state NMR system with the high spatial resolution and high sensitivity needed to implement scalable nuclear-spin-based qubits

Efficient gate control of spin-valve signals and Hanle signals in GaAs channel with p-i-n junction-type back-gate structure

Efficient gate control of spin-valve signals and Hanle signals was achieved in a GaAs channel with a p-i-n back-gate structure. Experiments showed that the amplitude of the spin-valve signal (Delta V-NL) under constant-injection-current conditions increased for a cross nonlocal geometry when the channel was depleted by the gate voltage (V-G). In contrast, the V-G dependence of Delta V-NL for a nonlocal geometry was complicated. The gate modulation efficiency of spin signals was approximately 50 times that with a graphene or Si channel

Effect of CoFe insertion in Co2MnSi/CoFe/n-GaAs junctions on spin injection properties

The CoFe thickness (t(CoFe)) dependence of spin injection efficiency was investigated for Co2MnSi/CoFe/n-GaAs junctions. The Delta V-NL/I value, which is a measure of spin injection efficiency, strongly depended on t(CoFe), where Delta V-NL is the amplitude of a nonlocal spin-valve signal, and I is an injection current. Importantly, the maximum value of Delta V-NL/I for a Co2MnSi/CoFe/n-GaAs junction was one order of magnitude higher than that for a CoFe/n-GaAs junction, indicating that a Co2MnSi electrode works as a highly polarized spin source. No clear spin signal, on the other hand, was observed for a Co2MnSi/n-GaAs junction due to diffusion of Mn atoms into the GaAs channel. Secondary ion mass spectrometry analysis indicated that the CoFe insertion effectively suppressed the diffusion of Mn into GaAs, resulting in improved spin injection properties compared with those for a Co2MnSi/n-GaAs junction. (C) 2014 AIP Publishing LLC