Destabilization of the cooperative Jahn-Teller effect in Sr0.9Ce0.1MnO3 by Cr-doping

The structural study of Sr0.9Ce0.1Mn1-yCryO3 (y=0, 0.05, and 0.10) has been carried out by X-ray diffraction. For undoped sample Sr0.9Ce0.1MnO3, it undergoes a first-order structural transition accompanied by Jahn-Teller (JT) transition at TJT=320K. The JT transition temperature is reduced in Cr-doped samples, becoming TJT=260K for y=0.10. The tetragonal I4/mcm structure is characterized by the JT distortion in MnO6 octahedra with the distortion mode Q3. With increasing Cr doping content, the deformation of MnO6 octahedra is weakened, showing that Cr doping destabilizes the JT effect. In addition, elastic properties measurement indicates that a large softening of Young's modulus occurs in the vicinity of TJT, which has been interpreted in terms of the strong electron-phonon coupling originating from the JT effect.