We report a spectacularly high orbital/charge ordering temperature Tco = 475K, in Bi1/2Sr1/2MnO3. The charges order approximately 350K above the temperature predicted by the bandwidth tuning mechanism in the Ln1/2(Ca, Sr)1/2MnO3 family. This transition takes place 150K above that in Bi1/2Ca1/2MnO3 which is much more distorted. Strikingly, the TCO variation along the Bi1/2(Ca1-ySry)1/2MnO3 series (0 < ∼ y <∼ 1) is not monotonous but TCO suddenly jumps 150K for y≳0.5 compositions. Neutron and synchrotron diffraction data allow us to propose a new mechanism to justify this behavior. For compositions with high Sr content, the manifestation of the 6s2 character of the Bi3+ lone pair seems to markedly favor the charge ordering. © 2001 The American Physical Society.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 22 Jan 2001|