Charge transfer and antiferromagnetic insulator phase in SrRu1-xCrxO3 perovskites: Solid solutions between two itinerant electron oxides

A full range of SrRu1-xCrxO3 perovskite solid solutions (0 < x < 1) has been prepared using high temperatures and pressures up to 10.5 GPa. The structure changes from orthorhombic Pbnm at low x through a previously unreported rhombohedral R (E) over barc phase at x=0.4 to cubic Pm (3) over barm for 0.5 < x < 1. No Cr/Ru order is evidenced at any x. A substantial Ru4++Cr4+-> Ru5++Cr3+ charge transfer is evidenced by a volume discontinuity close to x=0.5. Low Cr-doped materials (x < 0.3) are itinerant, and ferromagnetic below 160-190 K, and x > 0.7 materials are itinerant and Pauli paramagnetic, but a substantial insulating region is found between these limits. Neutron diffraction shows the x=0.4 material to be antiferromagnetic with a high Neel temperature similar to 400 K and a saturated moment of 1.7 mu(B), despite the large Cr/Ru disorder. A 50 K magnetic transition and a low temperature structural phase change to orthorhombic Imma symmetry have been discovered in SrCrO3, suggesting that the ground state of this simple perovskite is more complex than was previously assumed.