2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009;
Pittsburgh, Pennsylvania
Session A22: Focus Session: Spins in Group III-V and II-VI Semiconductors
8:00 AM–11:00 AM,
Monday, March 16, 2009
Room: 324
Sponsoring
Units:
GMAG DMP FIAP
Chair: Paul Crowell, University of Minnesota
Abstract ID: BAPS.2009.MAR.A22.5
Abstract: A22.00005 : The importance of Fe interface states for ferromagnet-semiconductor based spintronic devices
9:12 AM–9:48 AM
Preview Abstract
Abstract
Author:
Athanasios Chantis
(Theoretical Division, Los Alamos National Laboratory)
I present our recent theoretical studies
of the bias-controlled spin injection, detection sensitivity and
tunneling anisotropic magnetoresistance in
ferromagnetic-semiconductor tunnel junctions.
Using first-principles electron transport methods we have shown
that Fe 3{\it d} minority-spin
surface (interface) states are responsible for at least two
important effects for spin electronics. First, they can produce a
\emph{sizable} Tunneling Anisotropic
Magnetoresistance in magnetic tunnel junctions with a
\emph{single} Fe electrode. The effect is driven by a Rashba
shift of the resonant surface band when
the magnetization changes direction. This can introduce a new class
of spintronic devices, namely, Tunneling Magnetoresistance
junctions with a
single ferromagnetic electrode that can function at room
temperatures. Second, in Fe/GaAs(001) magnetic tunnel junctions
they produce
a \emph{strong} dependence of the tunneling current
spin-polarization on
applied electrical bias. A
dramatic \emph{sign reversal} within a voltage range of just a
few tenths of an eV
is found. This explains the observed sign reversal of
spin-polarization in
recent experiments of electrical spin injection in Fe/GaAs(001)
and related reversal of tunneling magnetoresistcance through
vertical
Fe/GaAs/Fe trilayers. We also present a theoretical
description of electrical spin-detection at a
ferromagnet/semiconductor interface.
We show that the sensitivity of the spin detector has
\emph{strong} bias dependence which,
in the general case, is \emph{dramatically different} from that
of the tunneling current
spin-polarization. We show that in realistic
ferromagnet/semiconductor junctions
this bias dependence can originate
from two distinct physical mechanisms:
1) the bias dependence of tunneling current spin-polarization,
which is of \emph{microscopic}
origin and depends on the specific properties of the
interface, and 2) the \emph{macroscopic} electron spin transport
properties in the
semiconductor. Our numerical results show that the magnitude of
the voltage signal can be tuned over a wide range from the second
effect {\it alone} and thus identifies a universal method for
enhancing electrical spin-detection
sensitivity in ferromagnet/semiconductor tunnel contacts.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2009.MAR.A22.5