Spin-glass transition in a system with competing ferromagnetic and antiferromagnetic interaction
1976; American Physical Society; Volume: 14; Issue: 9 Linguagem: Inglês
10.1103/physrevb.14.4224
ISSN0556-2805
AutoresM. Gitterman, Michael W. Klein,
Tópico(s)Material Dynamics and Properties
ResumoUsing the recently developed method of Edwards and Anderson we obtain the free energy for a system of spins interacting with an exchange potential having a distribution in the form of the sum of two Gaussians centered about $\ifmmode\pm\else\textpm\fi{}{J}_{0}$ with widths $J$. When $J\ensuremath{\ne}0$, the system undergoes a spin-glass transition only, with the ferromagnetic or antiferromagnetic phases absent. When $J=0$ the system shows no transition in the molecular-field approximation used even though ${J}_{0}$ is finite. For very low temperatures and for $\frac{J}{{J}_{0}}\ensuremath{\lesssim}\frac{1}{2}$ the method gives a negative specific heat and magnetic susceptibility. These unphysical results also arose in connection with the negative entropy obtained previously for spin glasses.
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