Investigation of magnetic exchange interactions in Cr-doped Ca 0.5 Sr 0.5 RuO 3

Abstract The value of Curie temperature ( T C ) and resistivity for Ca 0.5 Sr 0.5 Ru 1 − x Cr x O 3 are found to increase with increase in x from 0 to 0.1. The T C increases from 38 K to 107 K. In this work, we investigate the increment using spin polarised density functional theory. The compounds exhibit Griffiths phase. Our results show that to understand the behaviour of the increase in T C , it is important to consider not only the competing super exchange and super–super exchange interactions between Ru/Cr–Ru/Cr ion pairs but also the increment in the value of the magnetic moment due to the localized character of the dopant (Cr) ion. Our results suggest that the increased resistivity with Cr doping could be due to increased scattering rate and strong on-site coulomb repulsion due to Cr doping. It is also important to note that the behaviour of T C with the Ru–O–Ru bond angle is not in line with the functional form reported for ferrites, chromites and some ferromagnetic oxides. We believe that our results will be helpful in further exploring the origin of magnetism and transport on Cr doping in perovskite ruthenates.