Electron magnetic resonance (EMR) study of electron-hole asymmetry in La1−xCaxMnO3 manganites (x=0.2,0.8)

X-band EMR measurements on powdered samples of single-crystalline La0.8Ca0.2MnO3 and polycrystalline La0.2Ca0.8MnO3 manganites were carried out at 120⩽T⩽500 K aiming to study the effect of the electron-hole doping asymmetry in La1−xCaxMnO3 system. In the paramagnetic (PM) state both compounds differ in the nature of short-range magnetic orderings observed-clusters of double-exchange coupled Mn3+-Mn4+ ions and magneto-impurity-like clusters in the La0.8Ca0.2MnO3 and La0.2Ca0.8MnO3 compounds, respectively. Ferromagnetic ground state of La0.8Ca0.2MnO3 is characterized by the coexistence of orbitally ordered Mn3+ subsystem and Mn4+ with band-like carriers one, which are responsible for the multiline EMR spectra. Charge-ordered antiferromagnetic ground state of La0.2Ca0.8MnO3 causes a sharp decrease in intensity and then vanishing of the EMR signal observed in the PM region.