SHORT-RANGE SPIN CORRELATIONS IN THE CMR MATERIAL LA1.4SR1.6MN2O7

The (La1-xSrx)(2)Mn3O7 compounds are layered materials that exhibit hi gher magneto-resistance than the corresponding 3D manganite perovskite s. Quasi-elastic neutron scattering on a polycrystalline sample of La1 .4Sr1.6Mn2O7 shows that the spin-fluctuation spectrum of these layered CMR materials is qualitatively similar to those found in the perovski te manganites (La, Ca)MnO3; their concentration, lifetime, and coheren ce length increase as T decreases to T-c. Unlike the perovskites, we f ind a lower spin-diffusion constant above T-c of similar to 5 meV Angs trom(2). (C) 1998 Elsevier Science B.V. All rights reserved.