Systematic analysis of metamagnetic transitions in A-site disordered Sm0.5(Ca0.5−ySry)MnO3 compounds: A combined experimental and model Hamiltonian study

Abstract

We investigate the ultra-sharp jump in the isothermal magnetization and the resistivity in the polycrystalline Sm0.5(Ca0.5−ySry)MnO3(y = 0, 0.1, 0.2, 0.25, 0.3, 0.5) compounds. The critical field (Hcr), required for the ultra-sharp jump, decreases with the increase of ‘Sr’ concentration, i.e. with an increase of average A-site ionic radius 〈rA〉. In addition, The magneto-transport data indicate that the phase separation increases with the increase of 〈rA〉, i.e. with ’y’. Moreover, the dependency of Hcr 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. In parallel with experiments, we have carried out numerical calculations to understand the role of A-site disorder in the metamagnetic transition. 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. Overall, our combined study comprising of several materials with different composition of A-site reveal the fact that how and why certain A-type disorder produces prominent metamagnetic transition.