Abstract
The bicritical point occurring in disordered spin-flop antiferromagnets is novel in two respects: (i) The critical exponents are, to all orders in epsilon =6-d, those of an Ising system in a random ordering field; (ii) In contrast to the pure case, the upper (u) and lower (l) phase boundaries are described by different shift exponents, psi u> psi 1. The upper shift exponent psi u is equal to the crossover exponent phi = gamma (1+ epsilon 2/36+...), where epsilon =6-d and gamma is the staggered susceptibility exponent. The lower shift exponent is unity, to all orders in epsilon .