20,520 research outputs found
Spintronic magnetic anisotropy
An attractive feature of magnetic adatoms and molecules for nanoscale
applications is their superparamagnetism, the preferred alignment of their spin
along an easy axis preventing undesired spin reversal. The underlying magnetic
anisotropy barrier --a quadrupolar energy splitting-- is internally generated
by spin-orbit interaction and can nowadays be probed by electronic transport.
Here we predict that in a much broader class of quantum-dot systems with spin
larger than one-half, superparamagnetism may arise without spin-orbit
interaction: by attaching ferromagnets a spintronic exchange field of
quadrupolar nature is generated locally. It can be observed in conductance
measurements and surprisingly leads to enhanced spin filtering even in a state
with zero average spin. Analogously to the spintronic dipolar exchange field,
responsible for a local spin torque, the effect is susceptible to electric
control and increases with tunnel coupling as well as with spin polarization.Comment: 6 pages with 4 figures + 26 pages of Supplementary Informatio
Modification of spintronic terahertz emitter performance through defect engineering
Spintronic ferromagnetic/non-magnetic heterostructures are novel sources for
the generation of THz radiation based on spin-to-charge conversion in the
layers. The key technological and scientific challenge of THz spintronic
emitters is to increase their intensity and frequency bandwidth. Our work
reveals the factors to engineer spintronic Terahertz generation by introducing
the scattering lifetime and the interface transmission for spin polarized,
non-equilibrium electrons. We clarify the influence of the electron-defect
scattering lifetime on the spectral shape and the interface transmission on the
THz amplitude, and how this is linked to structural defects of bilayer
emitters. The results of our study define a roadmap of the properties of
emitted as well as detected THz-pulse shapes and spectra that is essential for
future applications of metallic spintronic THz emitters.Comment: 33 pages, 13 figure
Graphene-based spintronic components
A major challenge of spintronics is in generating, controlling and detecting
spin-polarized current. Manipulation of spin-polarized current, in particular,
is difficult. We demonstrate here, based on calculated transport properties of
graphene nanoribbons, that nearly +-100% spin-polarized current can be
generated in zigzag graphene nanoribbons (ZGNRs) and tuned by a source-drain
voltage in the bipolar spin diode, in addition to magnetic configurations of
the electrodes. This unusual transport property is attributed to the intrinsic
transmission selection rule of the spin subbands near the Fermi level in ZGNRs.
The simultaneous control of spin current by the bias voltage and the magnetic
configurations of the electrodes provides an opportunity to implement a whole
range of spintronics devices. We propose theoretical designs for a complete set
of basic spintronic devices, including bipolar spin diode, transistor and logic
gates, based on ZGNRs.Comment: 14 pages, 4 figure
Hybrid Piezoelectric-Magnetic Neurons: A Proposal for Energy-Efficient Machine Learning
This paper proposes a spintronic neuron structure composed of a
heterostructure of magnets and a piezoelectric with a magnetic tunnel junction
(MTJ). The operation of the device is simulated using SPICE models. Simulation
results illustrate that the energy dissipation of the proposed neuron compared
to that of other spintronic neurons exhibits 70% improvement. Compared to CMOS
neurons, the proposed neuron occupies a smaller footprint area and operates
using less energy. Owing to its versatility and low-energy operation, the
proposed neuron is a promising candidate to be adopted in artificial neural
network (ANN) systems.Comment: Submitted to: ACM Southeast '1
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