<s>
RKKY	B-General_Concept
stands	O
for	O
Ruderman	O
–	O
Kittel	O
–	O
Kasuya	O
–	O
Yosida	O
.	O
</s>
<s>
The	O
RKKY	B-General_Concept
interaction	I-General_Concept
was	O
originally	O
proposed	O
by	O
Malvin	O
Ruderman	O
and	O
Charles	O
Kittel	O
of	O
the	O
University	O
of	O
California	O
,	O
Berkeley	O
,	O
as	O
a	O
means	O
of	O
explaining	O
unusually	O
broad	O
nuclear	O
spin	O
resonance	O
lines	O
that	O
had	O
been	O
observed	O
in	O
natural	O
metallic	O
silver	O
.	O
</s>
<s>
(	O
Alternatively	O
,	O
instead	O
of	O
nuclear	O
spins	O
coupling	O
to	O
conduction	O
spins	O
through	O
the	O
hyperfine	O
interaction	O
,	O
another	O
scenario	O
is	O
for	O
inner	O
electron	O
spins	O
to	O
couple	O
to	O
conduction	O
spins	O
through	O
the	O
exchange	B-General_Concept
interaction	I-General_Concept
.	O
)	O
</s>
<s>
The	O
derived	O
exchange	B-General_Concept
interaction	I-General_Concept
takes	O
the	O
following	O
form	O
:	O
</s>
<s>
Perhaps	O
the	O
most	O
significant	O
application	O
of	O
the	O
RKKY	B-General_Concept
theory	O
has	O
been	O
to	O
the	O
theory	O
of	O
giant	B-General_Concept
magnetoresistance	I-General_Concept
(	O
GMR	B-General_Concept
)	O
.	O
</s>
<s>
GMR	B-General_Concept
was	O
discovered	O
when	O
the	O
coupling	O
between	O
thin	O
layers	O
of	O
magnetic	O
materials	O
separated	O
by	O
a	O
non-magnetic	O
spacer	O
material	O
was	O
found	O
to	O
oscillate	O
between	O
ferromagnetic	O
and	O
antiferromagnetic	O
as	O
a	O
function	O
of	O
the	O
distance	O
between	O
the	O
layers	O
.	O
</s>
<s>
This	O
ferromagnetic/antiferromagnetic	O
oscillation	O
is	O
one	O
prediction	O
of	O
the	O
RKKY	B-General_Concept
theory	O
.	O
</s>
