Evidence for impurity-induced frustration in La2CuO4

TL;DR

This study investigates how non-magnetic impurities like Zn and Mg affect the magnetic properties of La2CuO4, revealing impurity-induced frustration that alters the antiferromagnetic order beyond simple dilution effects.

Contribution

It demonstrates that Zn doping induces magnetic frustration in La2CuO4, leading to a more rapid decrease in Néel temperature and spin stiffness than predicted by dilution models.

Findings

Zn doping causes greater suppression of T_N than Mg doping.

Impurity-induced frustration reduces spin stiffness more than dilution models predict.

Structural changes from doping influence exchange interactions.

Abstract

Zero-field muon spin rotation and magnetization measurements were performed in La2Cu{1-x}MxO4, for 0<x< 0.12, where Cu2+ is replaced either by M=Zn2+ or by M=Mg2+ spinless impurity. It is shown that while the doping dependence of the sublattice magnetization (M(x)) is nearly the same for both compounds, the N\'eel temperature (T_N(x)) decreases unambiguously more rapidly in the Zn-doped compound. This difference, not taken into account within a simple dilution model, is associated with the frustration induced by the Zn2+ impurity onto the Cu2+ antiferromagnetic lattice. In fact, from T_N(x) and M(x) the spin stiffness is derived and found to be reduced by Zn doping more significantly than expected within a dilution model. The effect of the structural modifications induced by doping on the exchange coupling is also discussed.