  Magnetic properties of polycrystalline CaMn1-xRuxO3 (x = 0 - 0.5) samples
were investigated in the temperature range 4.2 - 250 K, under external magnetic
field up to 15 kOe and under hydrostatic pressure up to 12 kbar. Transport
properties of the samples with x = 0.1, 0.2, 0.4, 0.5 were also investigated
under pressure up to 10 kbar. For x up to 0.4, the pressure was found to
suppress ferromagnetic correlations and to increase the resistivity, while for
x = 0.5 to act in the opposite way. While long ferromagnetic order is
completely suppressed, in small clusters ferromagnetic correlations probably
survive under pressure, as was revealed for CaMn0.9Ru0.1O3. The pressure effect
on the magnetic interactions and on the volume of ferromagnetic phase was found
to depend strongly on the Ru-content, and absolute value of the pressure
coefficient of spontaneous magnetization was found to decrease practically
linearly with increasing x in the range 0.1 < x < 0.5. The experimental data
are discussed in the frame of proposed energy-level diagram, which includes
magneto-impurity states at low and moderate Ru-doping and mixed-valence states
of Ru presented by a strongly-correlated t2g-like band at heavy Ru-doping. An
impact of disorder introduced by Ru-doping on the energy diagram and on derived
magnetic interactions is discussed. Predictions of the model regarding the
pressure effects on conductivity and temperature scales characteristic for
magnetic interactions are in reasonable agreement with experiment.
