Comparing the Effects of Varying Carrier Density and Isoelectronic Doping on Magnetic Properties of SrRuO_3

We change the carrier density by introducing Ru vacancies to form SrRu$_{1-v}$O$_3$ and introduce lattice distortions with the substitution of Ca to form Sr$_{1-x}$Ca$_x$RuO$_3$. The hyperfine field falls with increasing $x$ in Sr$_{1-x}$Ca$_x$RuO$_3$ and is less than 1T at x=0.8. For all values of x$<0.8$ the isomer shift and the quadrupole splitting remain unchanged. This fall in the value of the hyperfine field is consistent with what others have found for T$_c$. $T_c$ rapidly drops with increasing number of Ru vacancies so that T$_c$=45K when $v$=0.12 suggesting that carrier density has a stronger effect on T$_c$ than lattice distortions. The hyperfine field remains unchanged which may be explained by assuming that the polarization of the s-electrons responsible for the hyperfine field is due to localized d-electrons which give rise to the local moment present above T$_c$.