Reentrant Spin-Peierls Transition in Mg-Doped CuGeO_3

Abstract

We report a synchrotron x-ray scattering study of the diluted spin-Peierls (SP) material Cu_{1-x}Mg_xGeO_3. In a recent paper we have shown that the SP dimerization attains long-range order only for x < x_c = 0.022(0.001). Here we report that the SP transition is reentrant in the vicinity of the critical concentration x_c. This is manifested by broadening of the SP dimerization superlattice peaks below the reentrance temperature, T_r, which may mean either the complete loss of the long-range SP order or the development of a short-range ordered component within the long-range ordered SP state. Marked hysteresis and very large relaxation times are found in the samples with Mg concentrations in the vicinity of x_c. The reentrant transition is likely related to the competing Neel transition which occurs at a temperature similar to T_r. We argue that impurity-induced competing interchain interactions play an essential role in these phenomena.

5 pages, 4 embedded eps figures

References in corpus (2)

• The first-order phase transition between dimerized-antiferromagnetic and uniform-antiferromagnetic phases in Cu_(1-x)M_xGeO_3
• Structural Critical Scattering Study of Mg-Doped CuGeO3

Cited by in corpus (5)

• Separation of the magnetic phases at the Néel point in the diluted spin-Peierls magnet CuGeO3
• Effects of Disorder on Coexistence and Competition between Superconducting and Insulating States
• Simultaneous Charge Ordering and Spin Dimerization in Quasi-Two-Dimensional Quarter-Filled Ladders
• Enhancement of magnetic order in the incommensurate phase of Mg-doped CuGeO${}_3$
• Re-entrant Behavior and Gigantic Response in Disordered Spin-Peierls System