Disordered magnetic systems spin glasses

While some disordered magnetic systems do display spin-glass behavior, those that are not geometrically frustrated can behave in a fundamentally different way. In... 

In this section we discuss some disordered magnetic systems that do not fit well under any of the subject headings of the other sections in this review. am-DyAg (sect. 8.3.1) is the only amorphous f-moment material studied with [iSR to date, as the pyrochlores (sect. 8.3.2) are the only perfectly fhistrated f-magnets studied with p,SR. Quasicrystals (sect. 8.3.3) must stand somewhat separately because they have atomic structure that is neither amorphous nor merely disordered-crystalline. For a discussion of spin-glass-like behavior in Ce, Yb, and U strongly correlated electron materials, see sect. 9. 

The simulation of frustrated systems suffers from a similar tunneling problem as the simulation of first order phase transitions local minima in energy space are separated by barriers that grow with system size. While the multicanonical or optimized ensembles do not help with the NP-hard problems faced by spin glasses, they are efEcient in speeding up simulations of frustrated magnets without disorder. 

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