Crystals of the general composition {Y3−2xCa2x} [Fe2−yIny] (Fe3−xVx)O12were grown by the PbO flux method. Electron microprobe studies revealed zoning patterns of varyingxwithin these crystals, while the indium content was found uniform among all crystals from the same crucible. Averagexandywas determined by measuring the saturation magnetizationMsand the Curie temperature. Three series of crystals were produced withy=0, 0.11 and 0.35, andxranging from 0.19 to 0.82. Ferrimagnetic resonance between 4 and 300 K yielded the anisotropy constantsK1andK2. These single‐crystal data were supplemented by the results of line‐shape analysis of polycrystalline samples with lowMs. AtT=0, |K1(x) | is nonlinear with a maximum atx≈0.2. The reduced temperature dependence of the reduced anisotropy field was found independent of composition.