Structural, Magnetic and Electric Characteristics of Multiferroic CoFe&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt;/BNEuT Composite Thin Films Produced by Non-aqueous Sol-gel Process

Matsumoto

et al. 2021

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Microplate (MP) and microrod (MR)-type CoFe 2 O 4 /(Bi 3.25 Nd 0.65 Eu 0.10 )Ti 3 O 12 composite thin films were fabricated by a combination of reactive ion etching and metalorganic chemical vapor deposition. The effects of post-annealing temperature on the structural, magnetic, electrical, and magnetoelectric (ME) properties of the films were investigated. Based on the results, the optimal ferroelectric pillar structure to obtain a large ME voltage coefficient (α ME ) was determined. The electrical insulation properties for the films improved with increasing post-annealing temperature. On the other hand, magnetic and ferroelectric properties were degraded at high-temperature. Judging from the structural, magnetic, electric, and ME properties, the optimum post-annealing temperature was 700 °C. The shape of the ferroelectric layer had a significant influence on the ferroelectric properties and consequently on α ME . The MR shape exhibited a smaller clamping effect than the MP shape, producing a greater ME effect. The α ME for the MR-type film post-annealed at 700 °C was 5.5 mV cm −1 Oe −1 .

Section: Introductionmentioning

confidence: 99%

Effects of post-annealing temperature and micropillar shape on physical properties of micropillar-type multiferroic composite thin films

Matsumoto

et al. 2021

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“…25) In our previous studies, we succeeded in fabricating MF composite thin films consisting of a (Bi 3.25 Nd 0.65 Eu 0.10 )Ti 3 O 12 (BNEuT) nanoplate thin film with a strong a-axis orientation and a large remanent polarization (2P r = 66 μC cm −2 ) at room temperature, and a ferrimagnetic material. 26,27) Magnetic field−electric polarization control was attempted by applying a magnetic field in the in-plane direction, but no significant ME effect was observed. This was because the polarization axis in the in-plane direction of the ferroelectric material was the c-axis (P s = 4 μC cm −2 ), so the elastic interaction at the domain walls of the ferroelectric and ferromagnetic materials was small.…”

Section: Introductionmentioning

confidence: 99%

Effects of substrate temperature on physical properties of microrod-type multiferroic composite thin films fabricated by metal organic chemical vapor deposition

Ito

et al. 2020

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Microrod-type CoFe2O4(CFO)/Bi3.25Nd0.65Eu0.10Ti3O12(00ℓ) (BNEuT) composite thin films were fabricated by a combination of high-temperature sputtering, reactive ion etching, and metal organic chemical vapor deposition (MOCVD) on Pt(100)/MgO(100) substrates. The substrate temperature for MOCVD was varied from 450 °C to 600 °C to examine its effect on the structural, magnetic, and ferroelectric properties. The substrate temperature affects the compressive stress at the interface between the CFO and BNEuT. The surface morphology changed drastically above 550 °C. The room temperature magnetization–magnetic field hysteresis loops for the films showed clear ferromagnetic hysteresis loop and magnetic shape anisotropy. The room temperature polarization–electric field (P−E) hysteresis loops for the films showed a clear ferroelectric hysteresis loop, and slightly leaky P−E hysteresis loop. The coercive field increased slightly with increasing substrate temperature. Judging from the structural, ferromagnetic, and ferroelectric properties, the film deposited at 550 °C has potential as an excellent multiferroic material.

“…[3][4][5] Using these films as ferroelectric pillars, nanopillar-type multiferroic (MF) Fe 3 O 4 /BNEuT composite films were subsequently fabricated using metal organic chemical vapor deposition (MOCVD) [6][7][8][9][10][11] and CoFe 2 O 4 (CFO)/BNEuT composite films using a non-aqueous sol-gel method. 12,13) These films respectively contain conductive Fe 3 O 4 nanoparticles and ferrimagnetic CFO nanoparticles with a large magnetostriction constant (λ 100 = −250 × 10 −6 ) in the spaces (50-100 nm) between the BNEuT nanoplates. However, although an attempt was made to control the electric polarization by application of a magnetic field parallel to the substrate surface, it was difficult to observe a distinct magnetoelectric (ME) effect.…”

Section: Introductionmentioning

confidence: 99%

Fabrication and characterization of micropillar-type multiferroic composite thin films by metal organic chemical vapor deposition using a ferroelectric microplate structure

Ito

et al. 2019

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Using a a-axis-oriented epitaxial (Bi 3.25 Nd 0.65 Eu 0.10 )Ti 3 O 12 (BNEuT) thin films with a microplate-like shape as a ferroelectric pillar material, micropillar-type CoFe 2 O 4 (CFO)/BNEuT(h00)/Nb:TiO 2 (101) composite multiferroic films were fabricated by metal organic chemical vapor deposition. The deposition time was varied from 90-150 min to examine its effect on the structural, ferroelectric, and ferromagnetic characteristics of the films. All the films exhibit single-phase cobalt ferrite with a cubic inverse-spinel structure. The deposited CFO films have a similar columnar structure with a comparatively good step coverage of 37%-66%. The room-temperature magnetization−magnetic field hysteresis loop of the films showed a clear ferromagnetic hysteresis loop, and coercivity decreased from 1.1 to 0.9 kOe with increasing the deposition time. The roomtemperature polarization−electric field hysteresis loop of the films showed a ferroelectric hysteresis loop, and the effect of the leakage current was the smallest for a deposition time of 120 min.