2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009;
Pittsburgh, Pennsylvania
Session J29: Focus Session: Spin Currents in Metals - New and Miscellaneous Topics
11:15 AM–2:15 PM,
Tuesday, March 17, 2009
Room: 333
Sponsoring
Units:
GMAG DMP FIAP
Chair: Samir Garzon, University of South Carolina
Abstract ID: BAPS.2009.MAR.J29.6
Abstract: J29.00006 : Tunnel barrier enhanced voltage signals generated by magnetization precession of a single ferromagnetic layer*
12:15 PM–12:51 PM
Preview Abstract
Abstract
Author:
Takahiro Moriyama
(University of Delaware)
A variety of experimentally observed phenomena involving nonlocal
magnetization dynamics in magnetic multilayers are due to two
complementary effects: (i) the transfer of spin angular momentum
accompanying charge currents driven by the applied bias voltage
between ferromagnetic layers results in torques that (for
sufficiently high current densities) generate spontaneous
magnetization precession and switching; and (ii) the precessing
magnetization of a ferromagnet (FM) pumps spins into adjacent
normal metal layers (NM) with no applied bias. In particular, the
spin pumping effect is a promising candidate for realizing a spin
battery device [1] as a source of elusive pure spin currents (not
accompanied by any net charge transport) emitted at the FM/NM
interface, where steady magnetization precession of the FM layer
is sustained by the absorption of external rf radiation under the
FMR conditions. We report the electrical detection of
magnetization dynamics in an Al/AlO$_{x}$/Ni$_{80}$Fe$_{20}/$Cu
tunnel
junction,
where a Ni$_{80}$Fe$_{20}$ ferromagnetic layer is brought into
precession
under the ferromagnetic resonance (FMR) conditions. The dc
voltage generated across the junction by the precessing
ferromagnet is enhanced about an order of magnitude compared to
the voltage signal observed in Cu/FeNi/Pt structures [2]. A
structure of Cu (100nm)/Al (10nm)/AlO$_{x}$
(2.3nm)/Ni$_{80}$Fe$_{20}$
(20nm)/Cu (70nm)/Au (25nm) was fabricated on a Si substrate with
a 1$\mu$m
thick thermal oxide layer. The bottom-most 100 nm Cu layer was
patterned into a coplanar waveguide (CPW) and the rest of the
structure was patterned into a pillar structure on the signal
line of the CPW. Dc voltages $\sim\mu$V were observed in the
Al/AlO$_{x}$/Ni$_{80}$Fe$_{20}$/Cu tunnel junction when the
Ni$_{80}$Fe$_{20}$ is in the
ferromagnetic resonance. The dc voltages increase as the
precession cone angle and frequency increase. We discuss the
relation of this phenomenon to magnetic spin pumping and
speculate on other possible underlying mechanisms responsible for
the enhanced electrical signal.
\\[4pt]
[1] A. Brataas et al. PRB 66, 060404 (2002)\\[0pt]
[2] M. V. Costache et al. PRL 97, 216603 (2006)
*This work was supported by NSF DMR Grant No. 0405136, and DOE DE-FG02-07ER46374
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2009.MAR.J29.6