Ultrafast optical detection of magnetic inhomogeneity in ferromagnetic La_0.67Ca_0.33MnO₃

¹ Department of Physics & Astronomy, Hunter College, the City University of New York 695 Park Avenue, New York, NY 10065, USA
² Department of Optical Science and Engineering, and Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Fudan University - Shanghai 200433, China
³ Department of Applied Science, The College of William and Mary - Williamsburg, VA 23187, USA
⁴ Department of Physics, Pennsylvania State University - University Park, PA 16802, USA

^(a) hbzhao@fudan.edu.cn
^(b) yre@hunter.cuny.edu

Received: 26 June 2014
Accepted: 17 September 2014

Abstract

Optically excited spin wave resonances in ferromagnetic La_0.67Ca_0.33MnO₃ (LCMO) thin films are probed by subpicosecond Kerr-rotation experiments at 10 K. We identify an extra fundamental mode along with the confined spin wave modes, whose frequency and intensity are independent of film thickness, but depend strongly on the applied magnetic field. We attribute the origin of this mode to magnetic inhomogeneity at the FM ground state. Our results show that the picosecond time-resolved magneto-optical method is a powerful tool for detecting dynamic magnetic inhomogeneity in colossal magneto-resistance manganites.