Ferromagnetism and metallicity in (formula presented) (formula presented) Interplay between Ru doping and hydrostatic pressure

Magnetic properties of (formula presented) (formula presented) 0.04, and 0.08) are investigated in the temperature range 4.2-240 K, external magnetic fields up to 15 kOe and hydrostatic pressure up to 12 kbar. Transport properties of (formula presented) are also investigated in the temperature range 77-280 K and under pressure up to 10 kbar. It is found that for a pristine phase (formula presented) hydrostatic pressure increases the ferromagnetic domains embedded in an antiferromagnetic matrix, and slightly decreases the Néel temperature. The effect of pressure on the magnetic interactions depends upon Ru doping. For (formula presented) an applied pressure decreases both Curie and Néel temperatures, but enhances the ferromagnetic fraction. In the case of (formula presented) an applied pressure suppresses the ferromagnetic interactions and surprisingly increases the resistivity. To the best of our knowledge this is the first time that such an effect was observed in perovskites. All of the above observations are discussed in the context of phase separation.