Structural Critical Scattering Study of Mg-Doped CuGeO3

TL;DR

This study uses synchrotron x-ray scattering to investigate how magnesium doping affects the structural and magnetic properties of CuGeO3, revealing impurity-induced competing interactions that alter the spin-Peierls transition.

Contribution

It provides new insights into the effects of Mg doping on the spin-Peierls transition and the role of impurities in modifying magnetic and structural order in CuGeO3.

Findings

The temperature T_m for spin gap formation exceeds T_s for long-range order when x>0.

Long-range SP order exists only for x<x_c=0.021.

SP correlation length decreases rapidly with increasing Mg concentration.

Abstract

We report a synchrotron x-ray scattering study of the diluted spin-Peierls (SP) material Cu_(1-x)Mg_xGeO_3. We find that for x>0 the temperature T_m at which the spin gap is established is significantly higher than the temperature T_s at which the SP dimerization attains long-range order. The latter is observed only for x<x_c =0.021, while for x>x_c the SP correlation length quickly decreases with increasing x. We argue that impurity-induced competing interactions play a central role in these phenomena.