232 research outputs found
Large magnetoresistance effect due to spin-injection into a non-magnetic semiconductor
A novel magnetoresistance effect, due to the injection of a spin-polarized
electron current from a dilute magnetic into a non-magnetic semiconductor, is
presented. The effect results from the suppression of a spin channel in the
non-magnetic semiconductor and can theoretically yield a positive
magnetoresistance of 100%, when the spin flip length in the non-magnetic
semiconductor is sufficiently large. Experimentally, our devices exhibit up to
25% magnetoresistance.Comment: 3 figures, submitted for publicatio
Voltage-Controlled Spin Selection in a Magnetic Resonant Tunnelling Diode
We have fabricated all II-VI semiconductor resonant tunneling diodes based on
the (Zn,Mn,Be)Se material system, containing dilute magnetic material in the
quantum well, and studied their current-voltage characteristics. When subjected
to an external magnetic field the resulting spin splitting of the levels in the
quantum well leads to a splitting of the transmission resonance into two
separate peaks. This is interpreted as evidence of tunneling transport through
spin polarized levels, and could be the first step towards a voltage controlled
spin filter.Comment: To be published in Phys. Rev. Let
Molecular-beam epitaxy of (Zn,Mn)Se on Si(100)
We have investigated the growth by molecular-beam epitaxy of the II-VI
diluted magnetic semiconductor (Zn,Mn)Se on As-passivated Si(100) substrates.
The growth start has been optimized by using low-temperature epitaxy. Surface
properties were assessed by Nomarski and scanning electron microscopy. Optical
properties of (Zn,Mn)Se have been studied by photoluminescence and a giant
Zeeman splitting of up to 30 meV has been observed. Our observations indicate a
high crystalline quality of the epitaxial films.Comment: To be published in Applied Physics Letter
Fine structure of "zero-mode" Landau levels in HgTe/HgCdTe quantum wells
HgTe/HgCdTe quantum wells with the inverted band structure have been probed
using far infrared magneto-spectroscopy. Realistic calculations of Landau level
diagrams have been performed to identify the observed transitions.
Investigations have been greatly focused on the magnetic field dependence of
the peculiar pair of "zero-mode" Landau levels which characteristically split
from the upper conduction and bottom valence bands, and merge under the applied
magnetic field. The observed avoided crossing of these levels is tentatively
attributed to the bulk inversion asymmetry of zinc blend compounds.Comment: 5 pages, 4 figure
Tunneling magnetoresistance in devices based on epitaxial NiMnSb with uniaxial anisotropy
We demonstrate tunnel magnetoresistance (TMR) junctions based on a tri layer
system consisting of an epitaxial NiMnSb, aluminum oxide and CoFe tri layer.
The junctions show a tunnelling magnetoresistance of Delta R/R of 8.7% at room
temperature which increases to 14.7% at 4.2K. The layers show clear separate
switching and a small ferromagnetic coupling. A uniaxial in plane anisotropy in
the NiMnSb layer leads to different switching characteristics depending on the
direction in which the magnetic field is applied, an effect which can be used
for sensor applications.Comment: 8 pages, 3 figures, submitted to Appl. Phys. Let
- …