Intrinsic structural distortion and superexchange interaction in the orthorhombic rare-earth perovskites RCrO3

High-resolution neutron powder diffraction has been applied to determine the structural evolution in the orthorhombic perovskite RCrO3 family. The structural distortions observed have been found to be closely related to the dramatic variation in the magnetic ordering temperature T-N. In addition to the reduction in the orbital overlap integral that can account for the change in T-N in the RFeO3 family, the effect of t-e hybridization due to the structural distortions are responsible for the dramatic change in T-N across the RCrO3 family.