Coercivity and exchange bias of bismuth ferrite nanoparticles isolated by polymer coating

Abstract

Bismuth ferrite nanoparticles have been extensively investigated over the last few years due to their potential candidacy for application in future memory devices. However, all the work reported so far on bismuth ferrite nanoparticles is on agglomerated nanoparticles. Agglomerated particles can magnetically interact with each other. To utilize them for device application, it is useful to know the properties of the individual particles. Here, de-agglomeration of ∼75 nm bismuth ferrite nanoparticles is achieved by polyaniline coating on the surface. The structural and magnetic properties of agglomerated and de-agglomerated nanoparticles are compared. It is observed that there is a change in the lattice parameters and Fe-O-Fe and O-Bi-O bond angles due to polyaniline shell. The coercivity of the bismuth ferrite/polyaniline core shell particles is reduced as compared to pure and agglomerated bismuth ferrite particles. The observed changes in the magnetic properties of coated particles are attributed to the shell induced isolation of individual bismuth ferrite nanoparticles as well as structural changes due to polyaniline coating.

Tunable band gap and coercivity of bismuth ferrite–polyaniline core–shell nanoparticles: the role of shell thickness

“…2 also shows the magnication of partial 2q range from 31 to 33 degrees, which contains characteristic splitting of rhombohedral peak. The doublet near 32 remains same for all the samples and broadening is observed which can be attributed to decreasing values of lattice parameters due to incorporation of PANI 3 and it indicates that PANI might have formed the coordination with lattice oxygen, which has two major effects on BFO lattice (i) locally distort the crystal lattice of BFO by incorporation of PANI. Distortion of the local lattice is signicant factor for supporting the changes observed in optical properties.…”

“…This brings Fe-Fe ions closer and contributes towards the changes in magnetic properties. 3 The successful polymerization of aniline onto the surface of BFO was conrmed by Fourier Transform Infrared Spectroscopy (FTIR), as shown in Fig. 3.…”

“…BFO nanoparticles were synthesized using a so chemical route combined with post synthesis annealing, reported earlier. 3 Briey, it involves a reaction of Bi(NO 3 ) 3 $5H 2 O and Fe(NO 3 ) 3 $9H 2 O in the presence of tartaric acid at 353 K. The precipitate is heated in an oven at 423 K. Aer washing in dilute nitric acid ($17%) and ethanol, it is annealed at 873 K for 2 h. The annealed powder is washed in Milli-Q water and ethanol several times, and then completely dried. The sample is simply referred to as BFO nanoparticles.…”

Probing bismuth ferrite nanoparticles by hard x-ray photoemission: Anomalous occurrence of metallic bismuth

“…This has led to extensive research primarily focused on physical property optimization, for example, magnetic property, in BFO by tailoring size of NPs. [9][10][11][12] The work on NPs of BFO has shown that they have size dependent ferromagnetism. The appearance of ferromagnetism in BFO, which in the bulk form is basically a G-type antiferromagnetic material with canted spins on a spiral chain with period of $62 nm has been explained as due to abrupt termination of spiral, canted spin chain, as well as structural disorder due to the strain at surface.…”

“…17,18 BFO nanoparticles were synthesized using a soft chemical route combined with post synthesis annealing, reported earlier. 10,12 All the chemicals used are of analytical grade (99.9% purity). Synthesis involves a reaction of Bi(NO 3 ) 3 Á5H 2 O and Fe(NO 3 ) 3 Á9H 2 O in the presence of tartaric acid at 353 K, until the product is in sol-gel form.…”