Magnetism of the LTT phase of Eu-doped La2-xSrxCuO4

The ESR signal of Gd spin probes (0.5 at.%) as well as the static normal state susceptibility of Eu (J(Eu3+) = 0) doped La2-x-ySrxEuyCuO4 reveal pronounced changes of the Cu magnetism at the structural transition from the orthorhombic to the low-temperature tetragonal phase for all nonsuperconducting compositions. Both a jumplike decrease ofx as well as the ESR data show an increase of the in-plane magnetic correlation length in the LTT phase. From the Gd3+ 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 CuO2 spin system slows down to ~1010-1011 s-1 However, there is no static order above T~8 K in contrast to the LTT phase of Nd-doped La{2-x}SrxCuO4 with pinned stripe correlations.