SLOW ANTIFERROMAGNETIC DYNAMICS IN THE LOW-TEMPERATURE TETRAGONAL PHASE OF LA2-XSRXCUO4 AS REVEALED BY ESR OF GD SPIN PROBES

Measuring the electron spin resonance of Gd spin probes we have studie d the magnetic properties of the copper oxide planes in the low-temper ature tetragonal (LTT) phase of Eu-doped La2-xSrxCuO4. The data give e vidence that at particular levels of Sr and Eu doping the frequency of the antiferromagnetic fluctuations omega(sf) in the LTT phase dramati cally decreases at low temperatures by almost three orders of magnitud e. However, no static magnetic order has been found for T greater than or equal to 8 K, in contrast to the observation by neutron scattering of stripe ordering of spins below 50 K in a Nd-doped La2-xSrxCuO4 sin gle crystal. In our opinion, static order in the Nd-doped compound is induced due to the interaction between the Cu spins with the rare-eart h magnetic moments. Therefore, a characteristic property of the magnet ism in the LTT structural phase may not be static magnetic order at el evated temperatures but rather extremely slow antiferromagnetic dynami cs.