BEGIN:VCALENDAR
VERSION:2.0
PRODID:Data::ICal 0.22
BEGIN:VEVENT
DESCRIPTION:Jae-Ho Chung \, Korea University\n\nThe spintronics technology
requires materials that allow simultaneous control of the charge and the s
pin degrees of freedom. Recent efforts dedicated in search of such materia
ls have led us to the successful fabrication of artificial ferromagnetic s
emiconductor GaMnAs\, where doping of magnetic Mn2+ ions into insulating G
aAs results in robust ferromagnetism and semiconducting property at the sa
me time. In order to realize useful devices from magnetic semiconductors\,
however\, it is important to be able to control not only the magnetic pro
perties of individual layers but also interactions between them. Previousl
y the interactions between ferromagnetic GaMnAs layers across nonmagnetic
GaAs spacers have been observed to be ferromagnetic only. Since the RKKY i
nteraction in metallic magnetic multilayers is known to produce exchange o
scillations between ferromagnetic and antiferromagnetic (AFM) as a functio
n of layer thickness\, AFM interlayer exchange coupling has been expected
to be attainable also in semiconductor-based multilayers by enhancing carr
ier concentrations in the spacers.\n
\n
\nTo test this idea\, we hav
e fabricated GaMnAs-based multilayers with different carrier concentration
s and thicknesses in the spacers. Molecular beam epitaxy was used to depos
it 10 periods of Ga0.97Mn0.03As/GaAs on GaAs (001) substrates. In order to
increase the carrier concentration of selected samples\, Be doping at the
concentration of 1.2 x 1020 cm-3 was introduced in the nonmagnetic spacer
. Using polarized neutron reflectivity\, we indeed observed and confirmed
the occurrence of antiferromagnetic interlayer coupling in some of the sam
ples with Be-doped spacers. Their field cycling behavior clearly indicated
that the observed antiferromagnetic coupling is spontaneous and robust. A
ll of these samples showed GMR-like transitions in magnetotransport measur
ements. In contrast\, none of the samples without Be-doped spacers showed
such behavior. These results indicate that the interlayer exchange couplin
gs in GaMnAs-based ferromagnetic multilayers can be controlled via enginee
ring of the spacer properties.\n
DTSTART:20101111T210000Z
LOCATION:Physics Building\, Room 204
SUMMARY:Interlayer exchange couplings in Ga1-xMnxAs/GaAs diluted ferromagne
tic semiconductor multilayers
END:VEVENT
END:VCALENDAR