LOW-TEMPERATURE FIELD-DEPENDENT MAGNETIZATION OF LA0.7SR0.3MNO3

We report measurements of the magnetization of single crystalline La0. 7Sr0.3MnO3 for temperatures T < 25 K and in fields of 1 and 3 T. This material is a ferromagnetic metallic oxide which exhibits colossal mag netoresistance. We find that the field-dependent magnetization decreas es with temperature in a manner consistent with spin-wave excitations. That is, in zero field the magnetization would vary as M(0)-M(T)propo rtional to T-3/2, as opposed to T-2 which might be expected with singl e-particle excitations. From this we are able to extract a spin-wave s tiffness value of 154 +/- 5 meV Angstrom(2) which is in excellent agre ement with recent neutron scattering and spin-wave resonance results.