  Multiferroic materials have driven significant research interest due to their
promising technological potential. Developing new room-temperature
multiferroics and understanding their fundamental properties are important to
reveal unanticipated physical phenomena and potential applications. Here, a new
room temperature multiferroic nanocomposite comprised of an ordered
ferrimagnetic spinel LiFe5O8 (LFO) and a ferroelectric perovskite BiFeO3 (BFO)
is presented. We observed that lithium (Li)-doping in BFO favors the formation
of LFO spinel as a secondary phase during the synthesis of LixBi1-xFeO3
nanoceramics. Multimodal functional and chemical imaging methods are used to
map the relationship between doping-induced phase separation and local ferroic
properties in both the BFO-LFO composite ceramics and self-assembled
nanocomposite thin films. The energetics of phase separation in Li doped BFO
and the formation of BFO-LFO composites is supported by first principles
calculations. These findings shed light on Li-ion role in the formation of a
functionally important room temperature multiferroic and open a new approach in
the synthesis of light element doped nanocomposites.
