Magnetism of the LTT phase of Eu doped La_{2-x}Sr_xCuO_4

TL;DR

This study investigates how Eu doping influences the magnetic properties of La_{2-x}Sr_xCuO_4 during the structural transition to the LTT phase, revealing increased magnetic correlation lengths and slowed spin fluctuations without static order.

Contribution

It provides new insights into the magnetic behavior of Eu-doped La_{2-x}Sr_xCuO_4 in the LTT phase, highlighting differences from Nd-doped variants.

Findings

Magnetic correlation length increases up to over 100 lattice constants.

Spin fluctuation frequency slows down to 10^{10}-10^{11} sec^{-1}.

No static magnetic order observed above 8K.

Abstract

The ESR signal of Gd spin probes (0.5 at %) as well as the static normal state susceptibility of Eu (J(Eu^{3+})=0) doped La_{2-x-y}Sr_xEu_yCuO_4 reveal pronounced changes of the Cu magnetism at the structural transition from the orthorhombic to the low temperature tetragonal phase for all non-superconducting compositions. Both a jumplike decrease of \chi as well as the ESR data show an increase of the in-plane magnetic correlation length in the LTT phase. From the Gd^{3+} ESR linewidth we find that for specific Eu and Sr concentrations in the LTT phase the correlation length increases up to more than 100 lattice constants and the fluctuation frequency of the CuO_2 spin system slows down to 10^{10}- 10^{11}sec^{-1}. However, there is no static order above T ~ 8K in contrast to the LTT phase of Nd doped La_{2-x}Sr_xCuO_4 with pinned stripe correlations.