Effect of Mn and Ba Codoping on a Magnetic Spin Cycloid of Multiferroic Bismuth Ferrite Nanoparticles

Abstract

Bismuth ferrite (BFO) is the drosophila of research in multiferroic materials due to its simultaneous magnetic and electric ordering at room temperature. The unfortunate detail is its antiferromagnetic ordering, which practically cancels magnetization and magnetoelectric coupling of the crystals. To induce finite coupling, dopants have been introduced with a certain success so far. Nanoparticles (NPs) can additionally constrain the formation of the magnetic cycloid in BFO due to size confinement. Doping nanoparticles can thus potentially provide a sizeable magnetization of BFO, making applications in computer memories and hyperthermia cancer treatment feasible. We show that the codoping of BFO NPs by Ba and Mn balances the electrochemical equilibrium, reduces the particle size, and shifts the magnetic phase transition to lower temperatures. The ferroelectric properties are retained and the remanent magnetization is increased by 1 order of magnitude: Bi 0.95 Ba 0.05 Fe 0.95 Mn 0.05 O 3 possesses a remanent magnetization of 0.277 Am 2 /kg. Our Mossbauer studies reveal that two effects drive this increase: partial destruction of the spin cycloid due to Mn and increased spin canting due to Ba doping inducing local stress fields. This dopant combination and particular concentration improve the effective magnetization value exceptionally well.

Role of cooperative factors in the photocatalytic activity of Ba and Mn doped BiFeO3 nanoparticles

“…Ba and Mn co-doped BFO NPs (Bi 1Àx Ba x Fe 0.95 Mn 0.05 O 3 : x ¼ 0.00, 0.01, 0.03, 0.05) were synthesized by a modied wet chemical 'sol-gel route' assisted by a calcination step at 773 K. 14 Bismuth nitrate Bi(NO 3 ) 3 $5H Photocatalysis (PC) procedure 10 À5 M of methyl orange (MO) and rhodamine B (RhB) aqueous suspensions were prepared. To establish an adsorptiondesorption equilibrium between the dye and the photocatalyst, 50 ml of organic dye with 0.025 g of NPs were placed into a jacketed beaker in the dark for 30 minutes.…”

“…11,12 BFO and doped BFO nanoparticles (NPs) are ferroelectric materials. 13,14 It has been shown that in photoferroelectric materials 15 the spatial separation of electrons (e À ) and holes (h + ) and their transfer from bulk to the surface is assisted by the presence of intrinsic spontaneous polarization induce local electric elds known as depolarization elds. 16 The role of this intrinsic electric eld for charge carrier dynamics in the ferroelectric photocatalyst for the photocatalytic redox reactions is fascinating, but the mechanisms are still not understood.…”

“…27 A moderate amount of doping into BFO at both Bi-and Fesites affects its ferroelectric, magnetic and optical properties. 14,28 It has been shown that cation doping can reduce the particle size and alter the band gap of pristine BFO. 29 These fruitful changes increase the surface to volume ratio and enhance the visible light absorption of the NPs, which are important parameters for photocatalytic application.…”

“…It has been shown that these elements are easy to incorporate, and their doping bestows the properties of BFO. 14,42 The versatile oxidation state and similar ionic radius of Mn makes it one of the best transition metals to substitute Fe.…”

Strong Impact of Cr Doping on Structural and Magnetic Properties of Bi0.5La0.5Fe1−xCrxO3−δ

“…[19][20][21][22] Regarding chemical substitution, many studies have been carried out on the effect of codoping at both Bi and Fe sites on the ferroelectric and magnetic properties of BFO. [23][24][25][26][27][28] It is worth mentioning that La and Cr have usually been applied as dopants. Because of the differences in ion radius, substitution of La and Cr at Bi and Fe sites can lead to large lattice distortion, suppressing the spiral spin structure and inducing the FM phase in BFO.…”