ISING MAGNETS WITH FRUSTRATION - ZERO-TEMPERATURE PROPERTIES FROM SERIES EXPANSIONS

We study a quenched random Ising magnet with mixed nearest-neighbor exchange couplings ±J on the square (sq), triangular (t), and simple-cubic (sc) lattices. We derive expansions for the T=0 thermodynamic properties in the ferromagnetic phase in powers of the concentration p of antiferromagnetic couplings. Analysis of these series in the variable c, which measures the concentration of frustrated plaquettes, indicates that ferromagnetism disappears at a second-order phase transition with pc(sq)0.099, pc(t)=0.10-0.15, and pc(sc)=0.12-0.13. The square-lattice series, which are the best behaved, suggest that (i) the magnetization vanishes with a critical exponent βM(sq)0.066, and (ii) the phase for p>pc may exhibit Edwards-Anderson order. © 1979 The American Physical Society.