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15 May 2003

Volume 93, Issue 10, pp. 5855-8792

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Resonant suppression of exciton spin relaxation in Zn0.96Mn0.04Se/CdSe superlattices

I. A. Buyanova, G. Yu Rudko, W. M. Chen, A. A. Toropov, S. V. Sorokin, S. V. Ivanov, and P. S. Kop'ev

J. Appl. Phys. 93, 7352 (2003); http://dx.doi.org/10.1063/1.1556933 (3 pages) | Cited 1 time

Online Publication Date: 9 May 2003

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Spin relaxation processes in strained Zn0.96Mn0.04Se/CdSe superlattices are studied in detail by using hot photoluminescence combined with tunable excitation spectroscopy. A drastic enhancement in occupation of the upper-lying ∣+1/2,−3/2〉 state of the heavy-hole excitons is observed when excitation photon energy is resonantly tuned near an integer number of the LO phonon energy above the ∣+1/2,−3/2〉 state. Assuming the Boltzmann distribution between the excitonic states, the spin temperature of the excitons is deduced to be as high as 85 K, well above the lattice temperature of 2 K. The observed behavior provides experimental evidence for a surprisingly strong suppression of spin relaxation from the upper spin-split excitonic branch for small values of wave vector. © 2003 American Institute of Physics.
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73.21.Cd Superlattices
78.66.Hf II-VI semiconductors
78.55.Et II-VI semiconductors
71.35.Lk Collective effects (Bose effects, phase space filling, and excitonic phase transitions)
75.50.Pp Magnetic semiconductors
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Digitally doped magnetic resonant tunneling devices: High tunneling magnetoresistance systems

D. A. Stewart and M. van Schilfgaarde

J. Appl. Phys. 93, 7355 (2003); http://dx.doi.org/10.1063/1.1556934 (3 pages) | Cited 2 times

Online Publication Date: 9 May 2003

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Magnetic resonant tunneling devices (RTDs) have been recognized as one possible route to developing a near ideal spin valve. With the advent of dilute magnetic semiconductors, the ability to grow these devices using traditional semiconductor techniques provides a distinct advantage over present metal-based giant magnetoresistance devices. We examine the effect of replacing dilute magnetic semiconductor leads (GaMnAs) with Ga0.5Mn0.5As monolayers adjacent to the RTD structure. We examine transmission through a series of GaAs/AlAs RTDs using principal layer Green function technique in the linear muffin-tin orbital framework. Self-consistent calculations using a linear response technique are done for both nonmagnetic RTDs and ones with Mn doped layers outside the AlAs barriers. The Mn dopant layers lead to splitting of the transmission peaks in both the conduction and the valence bands. The transmission peaks shift as the quantum well width increases in accordance with quantum well states. In addition, transmission in the minority spin channel is suppressed as valence quantum well states move closer to the Fermi energy. Preliminary zero bias conductance calculations give tunneling magnetoresistance values in excess of 1000%. While this estimate does not include spin scattering sources such as spin-orbit coupling, the actual tunneling magnetoresistance should still be very high. © 2003 American Institute of Physics.
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85.75.Mm Spin polarized resonant tunnel junctions
75.47.De Giant magnetoresistance
75.47.Pq Other materials
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
72.25.Mk Spin transport through interfaces
73.20.At Surface states, band structure, electron density of states
75.50.Pp Magnetic semiconductors
71.15.Ap Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.)

Organic luminescent devices and magnetoelectronics

A. H. Davis and K. Bussmann

J. Appl. Phys. 93, 7358 (2003); http://dx.doi.org/10.1063/1.1540174 (3 pages) | Cited 31 times

Online Publication Date: 9 May 2003

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Developments in magnetoelectronics are advancing by combination of once disparate areas of research in magnetic materials, semiconductor electronics, and optoelectronics. We explore the integration of magnetic materials with organic semiconductors. Because small spin–orbit coupling in these materials minimizes spin relaxation, they may be useful in spintronic applications. Motivated by a theoretical investigation into spin-dependent exciton formation that predicts a magnetoluminescence valve effect, we attempt to manipulate spin-polarized holes and electrons in an effort to generate magnetic field dependent luminescence in organic light emitting diodes (OLEDs). We have fabricated various functional OLEDs consisting of ferromagnetic electrodes sandwiching a organic semiconducting bilayer, thus demonstrating that hole and electron injection from magnetic electrodes is possible. However, magnetic transition metal anodes produce higher turn-on voltages and significantly reduced lifetimes compared to indium–tin–oxide based OLED’s. © 2003 American Institute of Physics.
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85.60.Jb Light-emitting devices
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
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