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Mater Sci Nanotechnol 2017
Volume 1 Issue 3
Magnetic Materials 2017
October 09-10, 2017 London, UK
International Conference on
Koki Takanashi, Materials Science and Nanotechnology
Advanced spintronic materials based on
ordered alloys
M
aterials used for spintronic devices should satisfy the
following requirements like high spin polarization,
leading to high efficiency in spin injection and high
magnetoresistance, high magnetic anisotropy, leading
to perpendicular magnetization and thermal stability of
magnetization at reduced dimension and proper damping
constant, leading to the optimization of the influence of spin
transfer torque. It would be best to find a universal material
that satisfies all these requirements; however, it is not easy.
Starting from a material that satisfies one of each, usually,
the way to extend the function by some modification of the
material or to combine those materials might be adopted.
We are interested in ordered alloys for spintronics, because
some of ordered alloys show excellent functionalities such
as high spin polarization and high magnetic anisotropy,
and they are promising for the application to spintronics.
Our group has been working on half-metallic Heusler alloys
with high spin polarization, and demonstrated high CPP-
GMR, which will be promising for the application to read
heads in HDD. Co
2
MnSi/Ag/Co
2
MnSi, Co
2
FexMn
1-x
Si/Ag/
Co
2
FexMn
1-x
Si and Co
2
FexMn
1-x
Si/Ag-Mg/Co
2
FexMn
1-x
Si
epitaxial-layered structures were prepared by sputtering,
and fabricated into pillar-shape by EB lithography for CPP-
GMR measurements. The maximum MR ratio and the
areal resistance change (
∆
RA) obtained up to now are 62
% and 25 mΩ•µm2, respectively. CPP-GMR devices with
half-metallic Heusler alloys also show high performance
as spin torque oscillators (STOs) because of their low
magnetic damping. A very high Q value of 4000 has been
obtained with a power output of 10 nW.
Figure 1: Importance of ordered alloys for spintronic
devices.
Biography
Koki Takanashi received his BS, MS, and Ph.D. degrees in Physics from the
University of Tokyo. After postdoctoral research at Tohoku University, he joined the
faculty there and is now a Professor and the Director of the Institute for Materials
Research at Tohoku University. In 1994-1995 he was an Alexander von Humboldt
Research Fellow at the Forschunszentrum Jülich in Germany. He has published
over 350 papers and has receive numerous awards, including the Outstanding
Research Award (2004, Magnetic Society of Japan), Outstanding Paper Award
(2009, Japan Society of Applied Physics), Masumoto Hakaru Award (2011, Japan
Institute of Metals). Professor Takanashi was the leader of a national project in
Japan: “Creation and Control of Spin Current” (2007-2011). His research interests
include magnetism and magneto-transport in nanostructures, magnetic materials
for spintronics, and spin current phenomena.
koki@imr.tohoku.ac.jpKoki Takanashi
Tohoku University, Japan