The mechanism by which the multiple-band metal Sr2RuO4 is transformed to th
e antiferromagnetic insulator Ca2RuO4 by isovalent substitution is not yet
understood in derail, but strong electron correlations play a key role. In
an effort to probe the effect of the substitution, we have performed a stud
y of the Hall effect in the Ca2-xSrxRuO4 system. We argue that the results
give information on the Fermi surface topography, and hence place useful co
nstraints on theories of the evolution of the electronic structure with var
ying x.