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

Abstract X-band EMR measurements on powdered samples of single-crystalline La 0.8 Ca 0.2 MnO 3 and polycrystalline La 0.2 Ca 0.8 MnO 3 manganites were carried out at 120⩽ T ⩽500 K aiming to study the effect of the electron–hole doping asymmetry in La 1− x Ca x MnO 3 system. In the paramagnetic (PM) state both compounds differ in the nature of short-range magnetic orderings observed—clusters of double-exchange coupled Mn 3+ –Mn 4+ ions and magneto-impurity-like clusters in the La 0.8 Ca 0.2 MnO 3 and La 0.2 Ca 0.8 MnO 3 compounds, respectively. Ferromagnetic ground state of La 0.8 Ca 0.2 MnO 3 is characterized by the coexistence of orbitally ordered Mn 3+ subsystem and Mn 4+ with band-like carriers one, which are responsible for the multiline EMR spectra. Charge-ordered antiferromagnetic ground state of La 0.2 Ca 0.8 MnO 3 causes a sharp decrease in intensity and then vanishing of the EMR signal observed in the PM region.