Non-conventional ordering studied by magnetic resonance in Fe-doped manganites

Coexistence of ferromagnetic (FM) and paramagnetic (PM) phases in La0.7Pb0.3(Mn1−xFex)O3 (0.1⩽x⩽0.30.1⩽x⩽0.3) manganites is studied by the electron spin resonance (ESR) technique. Doping with Fe gives rise to a progressive decrease both in the low-temperature magnetic moment and magnetic order temperature values. Obtained spectra show narrow resonance signals above Curie temperature that transform to asymmetric Dyson-like signals as temperature decreases. The evolution of line width with temperature shows minima that correlate directly with the obtained paramagnetic Curie temperatures. Analysis of spectra above and below magnetic order temperatures reveals features of complex PM to FM transitions and coexistence of both type of phases in a wide range of temperatures.