Competition between Spin-Peierls Phase and Three-Dimensional Antiferromagnetic Order in CuGe _{1- <i>x</i>} Si _<i>x</i> O ₃

Abstract

We have performed magnetic-susceptibility measurements and Cu nuclear-magnetic-resonance studies on single crystals of the quasi-one-dimensional antiferromagnet CuGe1-xSixO3, with 0 ⩽ x ⩽ 0.1. The Si doping has a drastic effect on the spin-Peierls temperature TSP which decreases at TSP (x)/TSP (0) ≅ 1-50x at low Si concentrations. For x ⩾ 0.005, three-dimensional antiferromagnetic order with an easy axis along the Cu chains takes place below a well-defined Néel temperature TN. A qualitative interpretation of the phase diagram (T, x) is given.