Magnetic susceptibility of diluted pyrochlore and SrCr9-9xGa3+9xO19 antiferromagnets

We investigate the magnetic susceptibility of the classical Heisenberg anti ferromagnet with nearest-neighbor interactions on the geometrically frustra ted pyrochlore lattice, for a pure system and in the presence of dilution w ith nonmagnetic ions. Using the fact that the con-elation length in this sy stem for small dilution is always short, we obtain an approximate but accur ate expression for the magnetic susceptibility at all temperatures. We exte nd this theory to the compound SrCr9-9xGa3+9xO19 and provide an explanation of the phenomenological model recently proposed by Schiffer and Daruka [Ph ys. Rev. B 56, 13712(1997)].