Evolution from Griffiths like phase to non-Griffiths like phase with Y doping in [formula omitted

Abstract

Detailed analysis of the temperature dependent dc susceptibility data shows the modification from the Griffiths like phase (GP) to non-Griffiths like phase (non-GP) in (La1-xYx)0.7Ca0.3MnO3(x=0,0.3,0.4,0.5,0.6) compounds with x. The existence of non-Griffiths phase is revealed from the upward deviation of the inverse susceptibility (1/χ) versus temperature plot from the Curie-Weiss behavior for the compounds with x⩾0.5. Whereas Griffiths phase is identified from the downturn of 1/χ versus T plot from the Curie-Weiss line in the compounds with x=0.3,0.4. The increased lattice distortion (with x) decreases the M-O-Mn bond angle and at the same time increase the electron-phonon (e-ph) coupling which in turn decreases the ferromagnetic double exchange (DE) interactions and enhances the effective short-range antiferromagnetic superexchange interactions between Mn3+/Mn3+ and Mn4+/Mn4+ ions above the Curie temperature (TC). The enhancement of this short-range antiferromagnetic (SR-AFM) interactions have been attributed to the conversions from GP to non-GP phase. The increased SR-AFM interactions with Y doping has also been substantiated from the magnetocaloric study.