Magnetoelastic coupling in La_(0.7)Ca_(0.3)MnO_(3)/BaTiO_(3) ultrathin films

Abstract

The magnetism of La_(0.7)Ca_(0.3)MnO_(3) (LCMO) epitaxial thin films grown on SrTiO_(3) (STO) and BaTiO_(3) (BTO) substrates is studied using polarized neutron reflectometry (PNR) and ferromagnetic resonance (FMR) techniques. In LCMO/BTO, PNR reveals a strongly suppressed magnetization of 300 kA/m, equivalent to a magnetic moment of 2 μB/Mn, throughout the LCMO layer, amounting to half the expected value. The largest suppression occurs near the interface with BTO, with magnetization values of 50 kA/m, equivalent to 0.3 μB/Mn. FMR is observable at 8.9 GHz only around the [110] crystallographic direction in thin LCMO/BTO. The resonance barely shifts as the applied field is rotated away from [110]. The FMR results are analyzed in terms of magnetoelastic anisotropy and compared to LCMO/STO grown under the same conditions. A two-layer magnetization model is proposed, based on strong out-of-plane anisotropy near the BTO interface and shown to qualitatively explain the main characteristics of the FMR results.