Evidence of phase separation in a (La,Pr,Ca)MnO₃ thin film by ferromagnetic resonance.

Phase separation (PS) in (La,Pr,Ca)MnO3 (LPCMO) manganites is the responsible for the colossal magnetoresistance (CMR) and a complex phase diagram for these systems [1]. The PS in the LPCMO between a ferromagnetic metal (FMM) phase and an antiferromagnetic charge-ordering insulator (AFM-COI) phase could be: (i) a fluid phase separation (FPS) between FMM and AFM-COI, both with a dynamic fluid-like behavior or (ii) a static phase separation (SPS) at lower temperatures with a glassy behavior [2]. The FPS to SPS transition could be a glass-like one associated to a strain-liquid to strain-glass transition [3]. Here we report ferromagnetic resonance (FMR) and transport measurements on a LPCMO thin film across the FPS to SPS transition. Changes in the FMR signal allow to identify the possible temperature ranges for the FPS and SPS states. We confirm by micromagnetic simulations that percolation paths of FMM phase give rise to additional resonance frequencies in the FPS state, which could open the possibility of magnonic control in the LPCMO thin films.

[1] M. Uehara et. al. Nature 399, 561–564 (1999).
[2] W. Wu et al. Nat. Mater. 5, 881–886 (2006).
[3] P.A. Sharma et. al. Phys. Rev. B. 71, (2005).