Evidence of strong disorder in both the ferromagnetic and antoferromagnetic phases of SrRu$_{1-x}$Mn$_x$O$_3$ using the M\"{o}ssbauer Effect*

We investigate the magnetism and disorder in powder samples of SrRu$_{1-x}$Mn$_x$O$_3$ and find significant changes in the M\"{o}ssbauer spectra even at very low values of $x$. At $x=0.1$, although the width of the spectrum is consistent with a hyperfine field $\simeq 32 T$, which is similar to that of SrRuO$_3$(33T), a single site fit fails, suggesting that there is a range of RuO$_6$ octahedra distortions. This sensitivity to doping is also seen in the spectrum of CaRu$_{0.8}$Cr$_{0.2}$O$_3$ where there is a $\sim$30T wide distribution of hyperfine fields. At $x=0.9$ the hyperfine field is due to antiferromagnetic order and is much larger, $50T$, than at $x=0.9$. The charge state of the Ru atom has also changed from $+4$ to close to $+5$. Again the spectrum is not that of a single Ru site in spite of the low density of Ru atoms in the sample.