NEW SLOW AND SHORT-RANGE MAGNETIC CORRELATIONS IN SUPERCONDUCTING LA2-XSRXCUO4

Inelastic neutron scattering measurements have been performed on high quality single crystals of La2-xSrxCuO4 in order to study the spin dyn amics of this compound. In addition to the well-established incommensu rate magnetic response, we show the existence of a new set of low ener gy excitations present in the whole superconducting region of the phas e diagram. This new feature of the dynamical cross section is characte rized; below about 10 K, by very short range (similar to 3 lattice spa cing) antiferromagnetic correlations and by a low energy scale of simi lar to 1 meV. At higher temperatures these fluctuations become nearly Q-independent. Different possible origins of these new spin correlatio ns are discussed.