Temperature versus concentration phase diagram of Mg- and Si-doped CuGeO3

We studied the temperature versus concentration(T-x) phase diagram in Cu1 - xMgxGeO3 by susceptibility measurements, synchrotron X-ray diffraction and neutron diffraction and the first-order phase transition between dimerized -antiferromagnetic and uniform-antiferromagnetic phases reported by Masuda et al. [Phys. Rev. Lett, 80 (1998) 4566] was established. We found that the T-x phase diagram of Cu1 - xMxGeO3(M = Zn,Ni) is similar to that of Cu1 - xMgxGeO3, while that of CuGe1 - xSixO3 is qualitatively different. (C) 2000 Elsevier Science B.V. All rights reserved.