Magnetoimpedance spectroscopy of phase-separated La0.5Ca0.5MnO3 polycrystalline manganites


Magnetoimpedance spectroscopy was carried out on phase-separated La0.5Ca0.5MnO3 polycrystalline manganites. The La0.5Ca0.5MnO3 powder was synthesized following an adapted sol-gel route. Structural and magnetic data showed the signs of phase coexistence of ferromagnetic (FM) Pnma and charge-ordered antiferromagnetic (CO-AFM) P2(1)/m phases. Magnetization vs. temperature (M vs. T) measurements revealed several magnetic transitions from the high temperature paramagnetic (PM) to an FM phase upon cooling (PM-FM) at approximate to 240 K, FM-AFM (approximate to 170 K) and AFM-FM (approximate to 100 K). Magnetic field (H)-dependent impedance spectroscopy data were collected from sintered pellets and fitted with an equivalent circuit model to separately analyze the different dielectric contributions from the grain boundary (GB) and the grain interior bulk areas. This allowed separating the GB and bulk magnetoresistance (MR), which was shown to amount to a maximum of approximate to 80% for both GB and bulk at H = 10 T near the metal-insulator transition (MIT) at approximate to 100 K. The GB resistance was found to be larger than the bulk resistance by a factor of approximate to 3, which implies that the direct current (DC) resistance and DC MR are dominated by contributions from the GBs. The magnetocapacitance (MC) effects detected were all found to be small below approximate to 3%, including in the presence of a CO phase.




Chemistry; Physics


Smari, M; Hamdi, R; Prado-Gonjal, J; Cortes-Gil, R; Dhahri, E; Mompean, F; Garcia-Hernandez, M; Schmidt, R



The authors wish to thank Maria Teresa Fernandez-Diaz for carrying out neutron diffraction experiments. They also thank the Institute Laue Langevin (ILL) for assigning neutron beam-time. They thank Jose Antonio Alonso for useful discussions, and Emilio Matesanz for thermodiffraction measurements. They thank Schmidt Scientific Support Services (SSSS) for help with the analysis of magneto-impedance spectroscopy data. J. P. G. acknowledges the MICINN in Spain for a Juan de la Cierva scholarship, the Comunidad de Madrid for a atraccion de talento fellowship and the European Commission for a Marie-Curie research fellowship. M. S. acknowledges funding from the Tunisian National Ministry of Higher Education, Scientific Research and Technology. Spanish MINECO grant MAT2017-87134-C2-2-R is also acknowledged.

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