Effects of high pressure, magnetic fields, and substitutions - ICMR ...
Effects of high pressure, magnetic fields, and substitutions - ICMR ...
Effects of high pressure, magnetic fields, and substitutions - ICMR ...
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2. Frustration due to competing interactions<br />
AFM<br />
E-type<br />
J 1<br />
>0 J 2<br />
>0<br />
Ground state energy (Ising limit):<br />
AF: N (J 2<br />
-J 1<br />
)<br />
In a simple Ising (Heisenberg) model<br />
<strong>of</strong> spins with AFM/FM first <strong>and</strong> AFM<br />
second neighbor interaction there is<br />
frustration <strong>and</strong> degeneracy near<br />
J 1<br />
=2J 2<br />
E-type: - N J 2<br />
Transition from AF to E-type at J 1<br />
= 2 J 2<br />
Same arguments hold for J 1<br />
< 0 (FM to E-type)<br />
This results in a complex phase<br />
diagram at T>0 with many<br />
commensurate <strong>and</strong> incommensurate<br />
phases<br />
The devil’s tree <strong>of</strong> the Ising<br />
model
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