  We report results of structural, magnetic and transport properties of single
crystal CaRu1-xCrxO3 (0&#8804;x&#8804;0.36) and SrRu1-xCrxO3
(0&#8804;x&#8804;0.30). Cr substitution as low as x=0.08 drives CaRu1-xCrxO3
from the paramagnetic state to an itinerant ferromagnetic state with
field-driven first-order metamagnetic transitions leading to a sizeable
saturation moment (~0.4&#61549;B/f.u.within the ab plane). The ferromagnetism
occurs abruptly and reaches as high as TC=123 K for x=0.22. The Cr-driven
ferromagnetism is highly anisotropic, suggesting an important role for
spin-orbit coupling. Lattice constant and magnetic measurements strongly
support the valence of the Cr as tetravalent (Cr4+, 3d2 configuration). Cr
substitution for Ru in SrRuO3 (TC=165 K) enhances the itinerant ferromagnetism,
with TC reaching 290 K for x=0.30, consistent with Cr-induced ferromagnetism in
paramagnetic CaRuO3. Preliminary pressure-dependent magnetization of
CaRu0.85Cr0.15O3 shows strong enhancement of the saturation magnetization (25%
for P~0.7 GPa). All results indicate a coupling of Ru 4d and Cr 3d electrons
that is unexpectedly favorable for itinerant ferromagnetism which often exists
delicately in the ruthenates.
