Ferromagnetic-like behavior of Bi_0.9La_0.1FeO₃-KBr nanocomposites

We studied magnetostatic response of the Bi_0.9La_0.1FeO₃- KBr composites (BLFO-KBr) consisting of nanosized (≈100 nm) ferrite Bi_0.9La_0.1FeO₃ (BLFO) conjugated with fine grinded ionic conducting KBr. When the fraction of KBr is rather small (less than 15 wt%) the magnetic response of the composite is very weak and similar to that observed for the BLFO (pure KBr matrix without Bi_1-xLa_xFeO₃ has no magnetic response as anticipated). However, when the fraction of KBr increases above 15%, the magnetic response of the composite changes substantially and the field dependence of magnetization reveals ferromagnetic-like hysteresis loop with a remanent magnetization about 0.14 emu/g and coercive field about 1.8 Tesla (at room temperature). Nothing similar to the ferromagnetic-like hysteresis loop can be observed in Bi_1-zLa_zFeO₃ ceramics with z ≤ 0.15, which magnetization quasi-linearly increases with magnetic field. Different physical mechanisms were considered to explain the unusual experimental results for BLFO-KBr nanocomposites, but only those among them, which are highly sensitive to the interaction of antiferromagnetic Bi_0.9La_0.1FeO₃ with ionic conductor KBr, can be relevant.