Light and Spins in III-V Ferromagnetic Semiconductors

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15 Νοε 2013 (πριν από 3 χρόνια και 7 μήνες)

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Light and Spins
in
III
-
V

F
errom
agnetic
S
emiconductors

Hiro Munekata

Tokyo Institute of Technology, Yokohama, Japan

e
-
mail : hiro@isl.titech.ac.jp



III
-
V ferromagn
e
tic
semiconductors

(FS)
,

such
as (In,Mn)As
[1,2] and (Ga,Mn)As
[
3,4
],
are the semiconducto
r alloys which c
on
tain a

large amount of magnetic ions (10
20
-
10
21

cm
-
3
)
in the III
-
V semiconductor
epitaxial

films. T
h
is
was realized
by
carrying out
the epitaxial
growth
at
substrate temperature
of
T
s



200


300

C

which is
far below the value
s

used for
the conventional epitaxial growth (
T
s



400
-

600
0

C)
. S
tud
ies
carried out for more than a
decade
have revealed
that various transition metal elements could be incorporated beyond the
solubility limit in
all
III
-
V host crystals by properly choosing
the

gr
owth conditions.


F
or the mid
-

and narrow gap III
-
V
FS
, Mn ions that occupy the group III sub
-
lattice sites
are electrically and magnetically active and form the spin
-
selective, acceptor

states near the
top of the valence band.
Th
is spin
-
selective

chara
cter causes
both Mn ions and valence bands
to be spin polarized when electrons (or

holes) are shared between the
acceptor and valence
bands
(hole
-
mediated
ferromagnetism)
.

This situation
mak
es

it possible to manipulate
Mn
spins
through carrier spins
by
the

optical
excitation
.




Since the first demonstration of optical inducement of ferromagnetic order in (In,Mn)As
in 1997 [5],
we have been pursuing optical
manipulation of
ferromagnetism
. One such
striking example is the experiment of
magnetization

rotatio
n
in
a
ferromagnetic
p
-
(Ga,Mn)As

layer
induced by the optical spin injection using circularly polarized light
[
6,7
].
Other
interesting

experiments are the
optically
-
induced precession of magnetization

[8]
and
ultra
-
fast demagnetization

[
9
] in femto
-

and pi
co
-
second time regime. These
studies

would
lead us to the understanding of direct pathways of energy and momentum
transfer

among
electron, lattice, spin subsystems, and development of knowledge for the ultrafast
manipulation of magnetism.


[1]
H. Munekata
,
et al.
,
Phys. Rev. Lett.

63
, 1849 (1989)
.

[2]
H. Munekata,
et al.
,

J. Cryst.
Growth

111
, 1011

(1991)
.

[
3
]
H. Ohno,
et al
.,
Appl.
Phys. Lett.
69,

363 (1996).

[
4
]
T. Hayashi,
et al.
,
J. Cryst.
Growth
175
/
176,

1063 (1997).

[5]
S. Koshihara,
et al.
,
Phys.
Re
v. Lett.
78
,

4617 (1997)
.

[6]
A. Oiwa,
et al.
, Phys.
Rev. Lett.
88,

137202 (2002).

[7] Y. Mitsumori,
et al
., Phys.
R
ev. B
69
, 033203 (2004).

[8]
A. Oiwa,
et al
.
, J. Superconductivity: Incorp
.

Novel Magnetism
18
, 9 (2005).

[
9
]
J. Wang,
et al
.,
Phys.
Rev. Le
tt.
95
, 167401
1
-
4
(2005).


Affiliation and Mail address:

Imaging Science and Engineering Laboratory, 4259
-
G2
-
13 Nagatsuta, Midori
-
ku, Yokohama
226
-
8502, JAPAN

E
-
mail: hiro@isl.titech.ac.jp

Phone: +81
-
45
-
924
-
5185 Fax: +81
-
45
-
924
-
5178



Photograph