Out-of-plane spin alighnment in ultrathin films of sodium-doped manganites as evidenced by FMR measurements

This work demonstrates ferromagnetic resonance (FMR) technique to study the magnetic anisotropy in ultrathin films of sodium-doped lanthanum manganites. The La<;sub>1-x<;/sub>Na<;sub>x<;/sub>MnO<;sub>3<;/sub> (x = 0.16) films (in what follows LNMO films) with a thickness d = 20 nm and dimensions 3×7 mm were prepared on single crystalline LaAlO₃(001) substrates by DC magnetron sputtering. The FMR studies were carried out in the temperature range 100-300 K with the use of X-band ELEXSYS E500 EPR spectrometer. The FMR measurements were performed at frequency v = 9.44 GHz for the case where the magnetic field was perpendicular to a film plane. Magnetization as a function of temperature was measured by means of a Faraday method.