  The gallium substituted and calcium deficient variants of geometrically
frustrated b-CaCr2O4, b-CaCr2-2xGa2xO4 (0.02<= x<= 0.25) and b-Ca1-yCr2O4
(0.075<= y<= 0.15), have been investigated by x-ray powder diffraction,
magnetization and specific heat measurements. This allows for a direct
comparison of the effects, in a geometrically frustrated magnet, of the static
disorder that arises from non-magnetic substitution and the dynamic disorder
that arises from hole doping. In both cases, disturbing the Cr3+ lattice
results in a reduction in the degree of magnetic frustration. On substitution
of Ga, which introduces disorder without creating holes, a gradual release of
spins from ordered antiferromagnetic states is observed. In contrast, in the
calcium deficient compounds the introduction of holes induces static
ferrimagnetic ordering and much stronger perturbations of the b-CaCr2O4 host.
