Complex Magnetic, Electrical and Magnetoresistance Properties of Coexisting Mn-Fe Order-Disorder Phase Derived From Nanocomposite Perovskite Oxides

Abstract

We present conceptually original study on temperature-controlled interfacial reactions inLa0.45Ca0.55MnO3-LaFeO3 nanocomposite. It highlights that the topotactic interfacial reactions can be utilized as an innovative and broader strategy for functional oxide design through the temperature controlled tuning of cation ordering. It provides the opportunity to rule out the charge and size limitation to attain the cation ordering phenomenon. Consequently, the cation ordering and associated magnetic properties canbe customized through regulation of the reaction temperature. Unusual ordering of Mn and Fehas been achieved in ceramic samples through the interfacial topotactic reaction between La0.45Ca0.55MnO3 and LaFeO3 (LCMO–LFO) in nanocomposite form. The ordering of Mn and Fe has been manifested in artificial superlattices of 1 : 1 LaMnO3-LaFeO3. The LCMO–LFO composite annealed at 700 and 800 ℃exhibits ordering of Mn and Fe with a ferromagnetic TC of 225 K in corroboration with the TC of 230 K in LaMnO3-LaFeO3 superlattice. The complete randomization of Mnand Fe in 1000 ℃ annealed LCMO–LFO composite revealed the lack of long range magnetic ordering. Whereas the 900 ℃ annealed LCMO–LFO nanocomposite has evidenced spectacular evolution of complex magnetic and electrical states having amalgamated features of low temperature ordered state and high temperature disorder phase. The coexisting order-disorder phases in 900 ℃ annealed LCMO–LFO nanocomposite exhibit emergence of Griffiths phase, negative magnetoresistance and preferred Mott variable range hopping type electrical conduction at high temperature. On the other hand, a tendency towards long-range ferromagnetic cluster formation and magnetic glassy state appear at lower temperatures. This partially ordered Mn-Fe based perovskite establishes a bridge between the ordered and disorder phases. This study unravels a potential deliberate route to design cation order/disorder functional ceramic materials through temperature controlled interfacial topotactic reaction in nanocomposite by over ruling the differential charge and size limitation to achieve cation ordering.