Room temperature multiferroicity of hexagonal LuFeO3 and its enhancement by co-doping in Lu0.9Co0.1Fe0.9Ti0.1O3 nanoparticle system

Abstract

Antiferromagnetic LuFeO3 can be good multiferroic by having ferroelectricity in its non-centrosymmetric hexagonal phase. But, it is hard to stabilize this metastable phase, preventing the stable orthorhombic phase. In this work, metastable hexagonal LuFeO3 (LFO) nanoparticle was stabilized in chemical sol-gel route in pure phase and co-doped with Co and Ti in the same route to synthesize Lu0.9Co0.1Fe0.9Ti0.1O3 (LCFTO) nanoparticles. Room temperature multiferroicity of bare LFO was established through relevant characterization. And motive behind the co-doping is to enhance the magnetoelectric behavior of the bare system to synthesize a new monophasic type II magnetoelectric multiferroic. Structural investigation by thorough Rietveld analyses of the recorded X-ray diffractograms, confirmed the formation of pure hexagonal (P63cm) phase of both bare and doped LFO. However, deviations in various structural & microstructural parameters were observed in the doped system, which is mainly responsible for the enhancement of magnetic and electric properties of the sample. Presence of antiferromagnetic transition at ∼604 K confirmed the room temperature magnetic ordering of bare LFO. Interestingly, LCFTO shows a drastic enhancement of magnetic property than the bare one in all concerns, where the maximum magnetization at the maximum applied field is enhanced by nearly 36 times at room temperature. Detailed high-temperature dielectric investigation shows, good dielectric strength (∼261) of LFO gets enhanced highly in LCFTO (∼1053) and a high relaxation time having negligible loss factor with an indication of ferro to paraelectric transition above room temperature. Current density vs. electric field (J-E) curve suggests the presence of polarization at room temperature with negligible leakage loss. Direct measurement of ferroelectric loop shows the ferroelectricity (Pmax∼0.064 µc/cm2) of bare LFO at room temperature and a well improvement in the doped LCFTO (Pmax∼0.151 µc/cm2). The presence of room temperature magnetoelectric coupling, confirmed by magnetocapacitance measurements, results in a high value (∼5 %) of magnetocapacitance in the doped system which is also much higher than the bare one (<∼1 %) as expected. All these properties confirm the magnetoelectric multiferroicity of bare h-LuFeO3 at room temperature. And, co-doping in hexagonal LuFeO3 nanoparticle system results in a considerable improvement in its magnetoelectric behavior, so this co-doped system can be a promising and potential magnetoelectric multiferroic for the future generation magnetoelectric devices.