<s>
Despite	O
sometimes	O
being	O
called	O
an	O
exchange	B-General_Concept
force	I-General_Concept
in	O
an	O
analogy	O
to	O
classical	O
force	O
,	O
it	O
is	O
not	O
a	O
true	O
force	O
as	O
it	O
lacks	O
a	O
force	O
carrier	O
.	O
</s>
<s>
For	O
fermions	O
,	O
this	O
interaction	O
is	O
sometimes	O
called	O
Pauli	O
repulsion	O
and	O
is	O
related	O
to	O
the	B-General_Concept
Pauli	I-General_Concept
exclusion	I-General_Concept
principle	I-General_Concept
.	O
</s>
<s>
The	O
exchange	O
interaction	O
is	O
sometimes	O
called	O
the	O
exchange	B-General_Concept
force	I-General_Concept
.	O
</s>
<s>
However	O
,	O
it	O
is	O
not	O
a	O
true	O
force	O
and	O
should	O
not	O
be	O
confused	O
with	O
the	O
exchange	B-General_Concept
forces	I-General_Concept
produced	O
by	O
the	O
exchange	O
of	O
force	O
carriers	O
,	O
such	O
as	O
the	O
electromagnetic	O
force	O
produced	O
between	O
two	O
electrons	O
by	O
the	O
exchange	O
of	O
a	O
photon	B-Application
,	O
or	O
the	O
strong	O
force	O
between	O
two	O
quarks	B-Operating_System
produced	O
by	O
the	O
exchange	O
of	O
a	O
gluon	O
.	O
</s>
<s>
Multiple	O
bosons	O
may	O
occupy	O
the	O
same	O
quantum	O
state	O
;	O
however	O
,	O
by	O
the	B-General_Concept
Pauli	I-General_Concept
exclusion	I-General_Concept
principle	I-General_Concept
,	O
no	O
two	O
fermions	O
can	O
occupy	O
the	O
same	O
state	O
.	O
</s>
<s>
Although	O
these	O
consequences	O
of	O
the	O
exchange	O
interaction	O
are	O
magnetic	O
in	O
nature	O
,	O
the	O
cause	O
is	O
not	O
;	O
it	O
is	O
due	O
primarily	O
to	O
electric	O
repulsion	O
and	O
the	B-General_Concept
Pauli	I-General_Concept
exclusion	I-General_Concept
principle	I-General_Concept
.	O
</s>
<s>
Normally	O
,	O
exchange	O
interactions	O
are	O
very	O
short-ranged	O
,	O
confined	O
to	O
electrons	O
in	O
orbitals	O
on	O
the	O
same	O
atom	O
(	O
intra-atomic	O
exchange	O
)	O
or	O
nearest	O
neighbor	O
atoms	O
(	O
direct	B-General_Concept
exchange	I-General_Concept
)	O
but	O
longer-ranged	O
interactions	O
can	O
occur	O
via	O
intermediary	O
atoms	O
and	O
this	O
is	O
termed	O
superexchange	B-General_Concept
.	O
</s>
<s>
rare-earth	O
systems	O
)	O
,	O
the	O
Ruderman	O
–	O
Kittel	O
–	O
Kasuya	O
–	O
Yosida	O
(	O
RKKY	B-General_Concept
)	O
model	O
is	O
the	O
currently	O
accepted	O
mechanism	O
.	O
</s>
