Magnetic correlations in the bilayer manganite La1.2Sr1.8Mn2O7

Neutron scattering has been used to study the magnetic correlations in the double-layer manganite La1.2Sr1.8Mn2O7, which exhibits colossal magnetoresistance in the vicinity of the ferromagnetic transition at Tc=112K. Over a large temperature range above Tc, there is evidence for two-dimensional magnetic correlations which peak in intensity at the transition. Although the in-plane correlations are predominantly ferromagnetic, a strong canting of spins in neighboring planes within the bilayers, at an angle that is dependent on both the temperature and magnetic field, is observed. There are indications of a crossover to three-dimensional critical scattering very close to Tc, but the nature of the phase transition has yet to be determined. copyright 1998 American Institute of Physics