Surface and bulk spin-wave resonances in La_0.7Mn_1.3O₃films

Abstract

In this work, we present the measurements of exchange-dominated nonpropagating surface and bulk spin-wave modes in the La-deficient epitaxial La0.7Mn1.3O3 films prepared by dc-magnetron sputtering. The angular and temperature dependences of the modes observed are discussed. The main result obtained is the observation of the spin-wave resonance (SWR) consisting of a series (17) of well resolved standing spin-wave modes in the perpendicular external magnetic field geometry. The surface spin-wave modes have been observed in manganites for the first time. As the magnetization is rotated out of perpendicular to the film surface, a `critical angle', φcr, is fixed, at which the surface and first spin-wave modes have been transformed into the uniform mode. It is shown that only the uniform mode exists in the region 0<φ<φcr. The surface mode data are consistent with the surface-inhomogeneity model in which the surface-anisotropy field acts on the surface spin. Possible origins of the surface anisotropy are discussed. Based on the temperature and angular dependences of SWR spectra, the main microscopic parameters (the spin-wave stiffness, exchange constant and g-factor value) are established.