Effect of A-site ionic radius on metamagnetic transition in charge ordered $S{m}_{0.5}(C{a}_{0.5-y}S{r}_y)Mn{O}_3$ compounds

Abstract

We investigate the ultra-sharp jump in the isothermal magnetization and the resistivity in the polycrystalline $S{m}_{0.5}(C{a}_{0.5-y}S{r}_y)Mn{O}_3$ $(y=0,0.1,0.2,0.25,0.3,0.5)$ compounds. The critical field $(H_{cr})$, required for the ultra-sharp jump, decreases with increase of `Sr' concentration, i.e. with increase of average A-site ionic radius $⟨r_A⟩$. The magnetotransport data indicate that the phase separation increases with the increase of $⟨r_A⟩$, i.e. with $y$. The dependency of $H_{cr}$ with magnetic field sweep rate reveals that the ultra-sharp jump from antiferromagnetic (AFM) state to the ferromagnetic (FM) state is of martensitic in nature. Our two-band double exchange model Hamiltonian calculations show that the `Sr' doping induces the ferromagnetic clusters in the antiferromagnetic insulating phase and in turn reduces the critical field. In the end we present a phenomenological picture obtained from our combined experimental and theoretical study.