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The high pressure behaviors of the two perovskite structures (hexagonal 6H-SrIrO3 and orthorhombic 3C-SrIrO3) have been studied in diamond anvil cells to 43 and 60 GPa, respectively, using synchrotron powder X-ray diffraction. 6H-SrIrO3 was first synthesized at ambient pressure and subsequently transformed into 3C-SrIrO3 in a large volume press at 8.8 GPa and 1000 °C. Both polymorphs were found to retain the initial symmetry up to the highest pressures measured, but in the case of 6H-SrIrO3, two anomalies were identified: a change in the axial compressibilities at 24 GPa and a change in both the axial and volume compressibilities at 32 GPa. Fitting a 3rd order Birch-Murnaghan equation of state to the obtained P-V data yielded bulk moduli of K0=151.5(12) GPa (fitted range 0

In order to analyze the effect of strain on the magnetic properties of narrow-band manganites, temperature-and field-dependent susceptibilities of about 8.5-nm-thick epitaxial Pr(0.7)Ca(0.3)MnO(3) films, respectively, grown on (001) and (110) SrTiO(3) substrates, have been compared. For ultrathin samples grown on (001) SrTiO(3), a bulklike cluster-glass magnetic behavior is found, indicative of the possible coexistence of antiferromagnetic and ferromagnetic phases. On the contrary, ultrathin films grown on (110) substrates show a robust ferromagnetism with a strong spontaneous magnetization of about 3.4 mu(B)/Mn atom along the easy axis. On the base of high-resolution reciprocal space mapping analyses performed by x-ray diffraction, the different behaviors are discussed in terms of the crystallographic constraints imposed by the epitaxy of Pr(0.7)Ca(0.3)MnO(3) on SrTiO(3). We suggest that for growth on (110) SrTiO(3), the tensile strain on the film c axis, lying within the substrate plane, favors the ferromagnetic phase, possibly by allowing a mixed occupancy and hybridization of both in-plane and out-of-plane e(g) orbitals. Our data allow to shed some physics of inhomogeneous states in manganites and on the nature of their ferromagnetic insulating state.