Magnetic phase diagram of the spin-Peierls and antiferromagnetic system

Neutron-diffraction experiments have been performed for (Formula presented) single crystals over a wide range of the Si concentration (0.4, 1.0, 1.7, 1.8, 2.1, 2.6, and 5.1 at. %) to study relations between the original spin-Peierls (SP) state and the antiferromagnetic (AF) long-range ordering induced by the Si doping. The SP state is strongly suppressed with the appearance of the AF state with the small amount of Si, and disappears at the concentration of around 2.5% at low temperatures. The AF phase persists throughout the concentration range studied here. Hence, the coexistence of these two states occurs in the concentration range up to around 2.5 at. % Si. The magnitudes of the AF magnetic moment and the lattice dimerization are given as a function of (Formula presented) The magnetic phase diagram obtained from these experiments has been compared with the previous reports on the Si and also Zn doping.