Correlations between the magnetic and structural properties of Ca-doped BiMnO3 - art. no. 134412

The Bi1-xCaxMnO3 system is known to exhibit charge ordering for a much broa der range of x than the La1-xCaxMnO3 system. However, the properties of Bi1 -xCaxMnO3 over the entire doping range are not well understood. We have per formed magnetization and resistivity measurements as well as x-ray absorpti on and x-ray diffraction measurements on Bi1-xCaxMnO3 to correlate structur al, magnetic, and transport properties. The system is insulating and antife rromagnetic for the entire range of x studied (x greater than or equal to0. 4) except near x similar to0.9, where we find a canted spin arrangement wit h approximately one Bohr magneton per Mn site. Detailed magnetization measu rements were performed as a function of field and temperature to explore th e net moment on the Mn sites as a function of x and reveal the charge order ing and Neel temperatures. X-ray absorption measurements reveal significant structural distortions of the Mn-O bond distributions with increasing Bi c ontent that correlates directly with increasing charge-ordering temperature s. Moreover, the x-ray diffraction data reveal peak splittings consistent w ith lower-symmetry cells as Bi content increases. These structural-magnetic correlations point to the importance of Mn-O distortions in stabilizing th e charge-ordered state in the manganites.