Ferromagnetic resonance study of Pr0.5(Ca1−xSrx)0.5MnO3

We study the competing phases at the crossover from localized to itinerant electronic behavior in the system Pr0.5(Ca1−xSrx)0.5MnO3, with 0.10⩽x⩽0.75. The study was performed by Q-band (35 GHz) electron spin resonance (ESR) spectroscopy. At room temperature, the samples show a single Lorentzian line centered at g=2.020 (5). Instead, at low temperature all the samples present a ferromagnetic resonance line (FMR) that coexists with a paramagnetic (PM) absorption. For x=0.15, the FMR absorption is observed at TC=200 K. This transition shifts to higher temperatures when x increases and for x=0.75, TC=260 K. The ferromagnetic metallic (FM) phase changes from a minority phase, when x<0.2, to a majority one, for x>0.2. We fit the temperature dependence of the ESR spectra considering an FM phase with uniaxial anisotropy that coexists with a PM phase. We have found that the anisotropy field of the FM phase increases with x.