UV-Irradiation-Enhanced Ferromagnetism in BaTiO<sub>3</sub>

Qin, Shubin; Liu, Duo; Zuo, Zhiyuan; Sang, Yuanhua; Zhang, Xiaolin; Zheng, Feifei; Liu, Hong; Xu, Xiangang

doi:10.1021/jz900131x

Cited by 49 publications

(25 citation statements)

References 31 publications

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“…Recently, Qin et al [21] improved the magnetic properties of semiconductors and found that UV irradiation could significantly enhance the magnetism of the (111) twinned BaTiO 3 crystallites. They demonstrated that magnetism might originate from the increase in oxygen vacancies and Ti 3+ cations formed by capturing an excited electron from Ti 4+ under UV irradiation.…”

Section: Introductionmentioning

confidence: 99%

Room-Temperature Magnetism of Ceria Nanocubes by Inductively Transferring Electrons to Ce Atoms from Nearby Oxygen Vacancy

Kang

Guo

et al. 2015

Nano-Micro Lett.

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Ceria (CeO2) nanocubes were synthesized by a hydrothermal method and weak ferromagnetism was observed in room temperature. After ultraviolet irradiation, the saturation magnetization was significantly enhanced from ~3.18 × 10−3 to ~1.89 × 10−2 emu g−1. This is due to the increase of oxygen vacancies in CeO2 structure which was confirmed by X-ray photoelectron spectra. The first-principle calculation with Vienna ab-initio simulation package was used to illustrate the enhanced ferromagnetism mechanism after calculating the density of states (DOSs) and partial density of states (PDOSs) of CeO2 without and with different oxygen vacancies. It was found that the increase of oxygen vacancies will enlarge the PDOSs of Ce 4f orbital and DOSs. Two electrons in one oxygen vacancy are respectively excited to 4f orbital of two Ce atoms neighboring the vacancy, making these electron spin directions on 4f orbitals of these two Ce atoms parallel. This superexchange interaction leads to the formation of ferromagnetism in CeO2 at room temperature. Our work indicates that ultraviolet irradiation is an effective method to enhance the magnetism of CeO2 nanocube, and the first-principle calculation can understand well the enhanced magnetism.

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Section: Introductionmentioning

confidence: 99%

Room-Temperature Magnetism of Ceria Nanocubes by Inductively Transferring Electrons to Ce Atoms from Nearby Oxygen Vacancy

Kang

Guo

et al. 2015

Nano-Micro Lett.

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“…The magnetism in these NP has been suggested to be intrinsic and originates from cation or anion vacancies at the surfaces of the NP. Very recently, it was reported from both experiments and first‐principles calculations that typical ferroelectric materials such as BaTiO 3 (BTO) and PbTiO 3 (PTO) become multiferroic when they are prepared at the nanoscale 1–8. So, nanocrystalline BTO offers a room‐temperature magnetic hysteresis as well as temperature‐dependent dielectric constant and a polarization.…”

mentioning

confidence: 99%

“…It is observed experimentally that the multiferroic nature emerges in an intermediate size range of nanocrystalline BTO. Whereas the ferromagnetism is arising from the oxygen vacancies or point defects at the surface of the NP the ferroelectricity is originated from the core of the material 1–3.…”

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confidence: 99%

Origin of ferromagnetism in BaTiO₃ nanoparticles

Bahoosh

Trimper

Wesselinowa

2011

Physica Rapid Research Ltrs

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Recently, there has been a great effort in studying magnetism in nonmagnetic semiconductors diluted with magnetic impurities due to possible applications in spinbased electronic systems. Moreover, nanoparticles (NP) of inorganic materials including otherwise nonmagnetic oxides such as CeO 2 , Al 2 O 3 , MgO, ZnO, In 2 O 3 and SnO 2 , nitrides, chalcogenides and other functional materials like superconductors and ferroelectrics were shown to be ferromagnetic at room temperature. The magnetism in these NP has been suggested to be intrinsic and originates from cation or anion vacancies at the surfaces of the NP. Very recently, it was reported from both experiments and firstprinciples calculations that typical ferroelectric materials such as BaTiO 3 (BTO) and PbTiO 3 (PTO) become multiferroic when they are prepared at the nanoscale [1 -8]. So, nanocrystalline BTO offers a room-temperature magnetic hysteresis as well as temperature-dependent dielectric constant and a polarization. Multiferroics that exhibit magnetoelectric coupling are widely discussed from quite different context, see [9 -12]. However, apart from a density functional calculation as vacancy-induced magnetism in BTO(001) thin films [13] a well accepted theoretical description of the ferroic properties of nanocrystalline BTO is still missing. In a previous paper [14] the static and dynamic properties of KH 2 PO 4 (KDP)-type and BTO-type ferroelectric NP have been reviewed. Based on that approach we propose a statistical model which reflects the multiferroic properties of BTO-NP. While the spontaneous polarization in a classic ferroelectric material like BTO is expected to diminish when the particle size is reduced [14-16], ferromagnetism cannot occur in bulk material [17]. It is observed experimentally that the multiferroic nature emerges in an intermediate size range of nanocrystalline BTO. Whereas the ferromagnetism is arising from the oxygen vacancies or point defects at the surface of the NP the ferroelectricity is originated from the core of the material [1][2][3].As demonstrated in [14] the Ising model in a transverse field is also appropriate to describe the properties of ferroelectric NP. The Hamiltonian reads e 1 2Since the ferroelectricity in BTO is originated from the off-centering of the Ti ions with respect to the cubic perovskite crystal we assume as the simplest model that there are two positions of the Ti atoms in a double-well potential. These two states are mapped on the S z -component of a pseudo spin-1/2 operator whereas the S x -component Based on a microscopic approach we demonstrate that the unexpected ferromagnetic properties of BaTiO 3 (BTO) or PTO observed recently at room temperature are due to oxygen vacancies at the surface of the nanocrystalline materials. Such vacancies lead to the appearance of Ti 3+ or Ti 2+ ions with nonzero net spin. The resulting different valence states composed of Ti 3+ or Ti 2+ offer a nonzero magnetization which decreases with increasing particle size. The system shows a multiferroic behavior belo...

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“…One is superexchange interaction withinCFO nanoparticles and another isexchange interaction atinterface of BTO and CFO phases. Thus thin layer of 17.5 nm of BTO in CFO@BTO sample favored the magnetization due to surface exchange interaction at the interface [21][22].However, surface spin canting occur due to thin layer of CFO nanoparticles in BTO@CFO nanocomposite that reduced magnetization. respectively.…”

Section: 2microscopic Analysismentioning

confidence: 97%

Structural, Magnetic, Dielectric and Energy Storage Analysis of CoFe2O4@BaTiO3 and BaTiO3@CoFe2O4 Core-Shell Nano- Composites

Sheoran¹,

Kumar²,

Kumar³

2020

Preprint

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Nano size spinel ferrite CoFe2O4 (CFO), ferroelectric BaTiO3 (BTO) and their core-shell nanocomposites BTO@CFO and CFO@BTO were synthesized using combination of chemical co-precipitation and sol-gel route respectively. The phase formation and crystallinity of bare CFO, BTO and their core-shell nanocomposites were verifiedviaX-ray diﬀraction pattern (XRD). High resolution transmission electron microscopy(HRTEM) revealed the core-shell structure of the nanocomposites.Magnetization measurements exhibitferromagnetic behaviour of all the samples except BTO in which superposition of weak ferromagnetic and diamagnetic response occurred due to its nanostructure. Magnetization versus temperature (M-T plot) measurements show anomaly near ferroelectric to paraelectric phase transition of BTO. Also,dielectric constant(ε¢) and tangent loss (tanδ) variation with respect to frequency (102 to 106 Hz) and temperature (300-700 K) were presented. ε¢-T curve of nanocomposites exhibit anomaly at the same temperature as observed in M-T plot of nanocomposites that indicate the inherent magneto-electric coupling in nanocomposites. Energy storage properties of BTO and nanocomposites have been examined via P-E loop analysis and confirmed that the sample CFO@BTO exhibit maximum energy storage efficiency.

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UV-Irradiation-Enhanced Ferromagnetism in BaTiO₃

Cited by 49 publications

References 31 publications

Room-Temperature Magnetism of Ceria Nanocubes by Inductively Transferring Electrons to Ce Atoms from Nearby Oxygen Vacancy

Room-Temperature Magnetism of Ceria Nanocubes by Inductively Transferring Electrons to Ce Atoms from Nearby Oxygen Vacancy

Origin of ferromagnetism in BaTiO₃ nanoparticles

Structural, Magnetic, Dielectric and Energy Storage Analysis of CoFe2O4@BaTiO3 and BaTiO3@CoFe2O4 Core-Shell Nano- Composites

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UV-Irradiation-Enhanced Ferromagnetism in BaTiO3

Cited by 49 publications

References 31 publications

Room-Temperature Magnetism of Ceria Nanocubes by Inductively Transferring Electrons to Ce Atoms from Nearby Oxygen Vacancy

Room-Temperature Magnetism of Ceria Nanocubes by Inductively Transferring Electrons to Ce Atoms from Nearby Oxygen Vacancy

Origin of ferromagnetism in BaTiO3 nanoparticles

Structural, Magnetic, Dielectric and Energy Storage Analysis of CoFe2O4@BaTiO3 and BaTiO3@CoFe2O4 Core-Shell Nano- Composites

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UV-Irradiation-Enhanced Ferromagnetism in BaTiO₃

Origin of ferromagnetism in BaTiO₃ nanoparticles