The duality between electric and magnetic dipoles inspires recent comparisons between ferronics and magnonics.Here we predict surface polarization waves or“ferrons”in ferroelectric insulators,taking the long-range d...The duality between electric and magnetic dipoles inspires recent comparisons between ferronics and magnonics.Here we predict surface polarization waves or“ferrons”in ferroelectric insulators,taking the long-range dipolar interaction into account.We predict properties that are strikingly different from the magnetic counterpart,i.e.the surface Damon-Eshbach magnons in ferromagnets.The dipolar interaction pushes the ferron branch with locked circular polarization and momentum to the ionic plasma frequency.The low-frequency modes are on the other hand in-plane polarized normal to their wave vectors.The strong anisotropy of the lower branch renders directional emissions of electric polarization and chiral near fields when activated by a focused laser beam,allowing optical routing in ferroelectric devices.展开更多
In this work the neutral-current scattering cross-section for neutrinos on electrons is calculated assuming that a massive Dirac neutrino is characterized by a phenomenological parameters, a charge radius 2> and th...In this work the neutral-current scattering cross-section for neutrinos on electrons is calculated assuming that a massive Dirac neutrino is characterized by a phenomenological parameters, a charge radius 2> and the right-handed currents are present in the framework of a Left-Right symmetric model (LR). Using the CHARM II result for the charge radius of the muon-neutrino |2>|<6.0×10-33cm2, we place a bound on -7.9×10-33cm2≤2>LR≤7.9×10-33cm2. We discuss the relationship between the electron neutral couplings gVeV and gVeA and the LR model parameters. We also estimate a bound on the heavy massive neutral vector boson mass MZR>650GeV of the LR model. These results have never been reported in the literature before and could have practical or theoretical interest, such as in the case of the neutrinos produced in core-collapse supernova explosions, that is to say, right-handed Dirac neutrinos emission from supernova core vLe-→vRe-.展开更多
We revisit the problem of the maximum masses of magnetized white dwarfs （WDs）. The impact of a strong magnetic field on the structure equations is addressed. The pressures become anisotropic due to the presence of t...We revisit the problem of the maximum masses of magnetized white dwarfs （WDs）. The impact of a strong magnetic field on the structure equations is addressed. The pressures become anisotropic due to the presence of the magnetic field and split into parallel and perpendicular components. We first construct stable solutions of the Tolman-Oppenheimer-Volkoff equations for parallel pressures and find that physical solutions vanish for the perpendicular pressure whenB ≥ 10^13 G. This fact estab- lishes an upper bound for a magnetic field and the stability of the configurations in the （quasi） spherical approximation. Our findings also indicate that it is not possible to obtain stable magnetized WDs with super-Chandrasekhar masses because the val- ues of the magnetic field needed for them are higher than this bound. To proceed into the anisotropic regime, we can apply results for structure equations appropriate for a cylindrical metric with anisotropic pressures that were derived in our previous work. From the solutions of the structure equations in cylindrical symmetry we have con- firmed the same bound for B- 10^13 G, since beyond this value no physical solutions are possible. Our tentative conclusion is that massive WDs with masses well beyond the Chandrasekhar limit do not constitute stable solutions and should not exist.展开更多
We investigated the evolutionary stages and disk properties of 211 young stellar objects（YSOs） across the Perseus cloud by modeling their broadband optical to mid-infrared（IR） spectral energy distribution（SED）. ...We investigated the evolutionary stages and disk properties of 211 young stellar objects（YSOs） across the Perseus cloud by modeling their broadband optical to mid-infrared（IR） spectral energy distribution（SED）. Our optical gri photometry data were obtained from the recently finished Purple Mountain Observatory Xuyi Schmidt Telescope Photometric Survey of the Galactic Anti-center（XSTPS-GAC）.About 81% of our sample fall into the Stage II phase which is characterized by having optically thick disks, while 14% into the Stage I phase characterized by having significant infalling envelopes, and the remaining 5% into the Stage Ⅲ phase characterized by having optically thin disks. The median stellar age and mass of the Perseus YSOs are 3.1 Myr and 0.3 M⊙ respectively. By exploring the relationships among the turnoff wave bands λturnoff（longward of which significant IR excesses above the stellar photosphere are observed）, the excess spectral index αexcess as determined for λ 〉 λturnoff, and the disk inner radius Rin（determined from SED modeling） for YSOs at different evolutionary stages, we found that the median and standard deviation of αexcess for YSOs with optically thick disks tend to increase withλturnoff, especially at λturnoff ≥5.8 μm, whereas the median fractional dust luminosities Ldust/L★ tend to decrease with increasing λturnoff. This points to an inside-out process of disk clearing for small dust grains. Moreover, a positive correlation between αexcess and Rin was found at α〉excess ～ 0 and R〉in～ 10 × the dust sublimation radius Rsub, irrespective of λturnoff, Ldust/L★ and disk flaring. This suggests that the outer disk flaring either does not evolve synchronously with the inside-out disk clearing of small dust grains or has little appreciable influence on the spectral slopes at λ〈～ 24 μm. About 23% of our YSO disks are classified as transitional disks, which haveλturnoff ≥ 5.8 μm and Ldust/L★ 〉 10-3. The transitional disks and full disks occupy distinctly different regions on the Ldust/L★ vs. αexcess diagram. Taking Ldust/L★ as an approximate discriminator of disks with（〉0.1） and without（〈0.1） considerable accretion activity, we found that 65% and 35% of the transitional disks may be consistent with being dominantly cleared by photoevaporation and dynamical interaction with giant planets respectively. None of our transitional disks have αexcess（〈0.0） or Ldust/L★（〉0.1） values that would otherwise be suggestive of disk clearing dominanted by grain growth.展开更多
In the solution of the Klein-Gordon equation for the shutter problem, we prove that, at internuclear distances, a relativistic beam of Pi-mesons has a probability density which oscillates in time in a similar way to t...In the solution of the Klein-Gordon equation for the shutter problem, we prove that, at internuclear distances, a relativistic beam of Pi-mesons has a probability density which oscillates in time in a similar way to the spatial dependence in optical Fresnel diffraction from a straight edge. However, for an extreme-relativistic beam, the Fresnel oscillations turn into quantum damped beat oscillations. We prove that quantum beat oscillations are the consequence, at extreme-relativistic velocities, of the interference between the initial incident wave function, and the Green’s function in the relativistic shutter problem. This is a pure quantum relativistic phenomenon.展开更多
Motivated by the recent result reported from LHC on the di-photon search from the Standard Model (SM) Higgs boson, we obtain limits on the anomalous couplings Hγγ and HZγ. We also perform a calculation at tree leve...Motivated by the recent result reported from LHC on the di-photon search from the Standard Model (SM) Higgs boson, we obtain limits on the anomalous couplings Hγγ and HZγ. We also perform a calculation at tree level of the decay widths as well as of the branching ratios for the reactions H → γγ and H → Zγ in the context of effective lagrangian for Higgs boson masses 115 ≤MH ≤ 130 GeV. We find that the decay widths and branching ratios from these reactions enhanced significantly due to the anomalous Hγγ and HZγ vertex, which would lead to measurable effects in Higgs signals at the LHC. Moreover, our results complement other studies on the channels H → γγ and H → Zγ.展开更多
In this study,we investigated the anomalous Chromomagnetic Dipole Moment(CMDM),denoted as μ_(q)^(BLHM),of light quarks q=(u,c,d,s,b) within the framework of the Bestest Little Higgs Model(BLHM)as an extension of the ...In this study,we investigated the anomalous Chromomagnetic Dipole Moment(CMDM),denoted as μ_(q)^(BLHM),of light quarks q=(u,c,d,s,b) within the framework of the Bestest Little Higgs Model(BLHM)as an extension of the Standard Model(SM).Our investigation encompassed novel interactions among the light quarks,heavy quark B,and heavy bosons (W'^(±),H^(±),φ^(±),η^(±))incorporating the extended Cabibbo-Kobayashi-Maskawa(CKM)matrix characteristic of the BLHM.We thoroughly explored the permissible parameter space,yielding a spectrum of CMDM values ranging from 10^(-10) to 10^(-3).展开更多
The effect of temperature on the electrical conductivity(σ)and Seebeck coefficient(S)of n-type vapor grown carbon nanofibers(CNFs)and poly(vinylidene fluoride)(PVDF)melt-mixed with 15 wt%of those CNFs is analyzed.At ...The effect of temperature on the electrical conductivity(σ)and Seebeck coefficient(S)of n-type vapor grown carbon nanofibers(CNFs)and poly(vinylidene fluoride)(PVDF)melt-mixed with 15 wt%of those CNFs is analyzed.At 40°C,the CNFs show stable n-type character(S=-4.8μV·K^(-1))with anσof ca.165 S·m^(-1),while the PVDF/CNF composite film shows anσof ca.9 S·m^(-1)and near-zero S(S=-0.5μV·K^(-1)).This experimental reduction in S is studied by the density functional tight binding(DFTB)method revealing a contact electron transfer from the CNFs to the PVDF in the interface.Moreover,in the temperature range from 40°C to 100°C,theσ(T)of the CNFs and PVDF/CNF film,successfully described by the 3D variable range hopping(VRH)model,is explained as consequence of a thermally activated backscattering mechanism.On the contrary,the S(T)from 40°C to 100°C of the PVDF/CNF film,which satisfactorily matches the model proposed for some multi-walled carbon nanotube(MWCNT)doped mats;however,it does not follow the increase in S(T)found for CNFs.All these findings are presented with the aim of discerning the role of these n-type vapor grown carbon nanofibers on theσand S of their melt-mixed polymer composites.展开更多
Ferroelectric ceramics are important materials with a wide range of industrial and commercial applications.Since the discovery of the phenomenon of ferroelectricity,they have been the heart and soul of several multibi...Ferroelectric ceramics are important materials with a wide range of industrial and commercial applications.Since the discovery of the phenomenon of ferroelectricity,they have been the heart and soul of several multibillion dollar industries,ranging from highdielectric-permittivity capacitors to developments in piezoelectric transducers,pyroelectric sensors,medical diagnostic transducers,electro-optical devices,etc.Materials based on barium titanate and lead zirconate titanate have dominated the field throughout their history.Actually,the ferroelectric ceramics from the Aurivillius family receive great attention due to their large remanent polarization,lead-free nature,relatively low processing temperatures,high Curie temperatures and excellent piezoelectric properties,which made them good candidates for multiple applications.This review presents a general overview of the progress in the studies on the ferroelectric ceramics from the Aurivillius family.The progress includes several aspects:(i)structural studies,(ii)dielectric and electric behavior,(iii)piezoelectricity,and(iv)pyroelectricity.展开更多
In this work,we intend to perform a detailed study on the crystallization process of PZT 53/47 nanostructured powders by starting out with an amorphous precursor synthesized by a sol-gel based solution.Our interests a...In this work,we intend to perform a detailed study on the crystallization process of PZT 53/47 nanostructured powders by starting out with an amorphous precursor synthesized by a sol-gel based solution.Our interests also lie in the feasibility for controlling the average grain size of the final structure in the submicron range on an ab initio basis.Purposely,Fourier transform infrared spectroscopy（FT-IR）,Raman（Stokes and Anti-Stokes）,X-ray diffraction（XRD） and scanning electron microscopy（SEM） are used to examine the microstructural characteristics based on previously reported differential thermal analysis/thermal gravimetric analysis（DTA/TGA） data.The results show a crystallization temperature of 800℃ to attain pure perovskite phase with excellent morphological quality,average grain size 〈DG〉〈 300 nm and with average crystallite size 〈DC〉〈15 nm.展开更多
BiFeO_(3)thin films were prepared using the chemical solution route on Pt/TiO_(2)/SiO_(2)/Si(100)substrates under different crystallization kinetics.The crystallization kinetic effects on the dielectric and electrical...BiFeO_(3)thin films were prepared using the chemical solution route on Pt/TiO_(2)/SiO_(2)/Si(100)substrates under different crystallization kinetics.The crystallization kinetic effects on the dielectric and electrical properties have been investigated.These properties included dielectric permittivity,electric modulus,electrical conductivity measurements as a function of the temperature(300-525 K)and frequency(10^(2)-10^(6)Hz),and leakage current measurements electric field range±30 kV/cm at room temperature.The differences observed in conductivity and current density of the BiFeO_(3)films were discussed in terms of possible defects induced by the crystallization kinetic.An anomalous relaxor-like dielectric behavior characterized by a broad maximum in the real dielectric permittivity as a function of temperature and the low-frequency dielectric dispersion has been observed.The nonexpected peaks in the real permittivity were accompanied by increasing at least four orders in the conductivity’s magnitude at high temperatures.The origin of the relaxor-like dielectric anomalies is discussed,suggesting that the dielectric permittivity peaks are artifacts due to carrier migration correlated to the onset of the Maxwell-Wagner effect.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant No.0214012051)the startup grant of Huazhong University of Science and Technology(Grants Nos.3004012185,3004012198)+5 种基金the financial support by JSPS KAKENHI(Grant Nos.19H00645,22H04965)financially supported in Brazil by Conselho Nacional de Desenvolvimento Científico e Tecnológico(CNPq)Coordenac ao de Aperfeicoamento de Pessoal de Nível Superior(CAPES)Financiadora de Estudos e Projetos(FINEP)Fundac ao de AmparoáCiencia e Tecnologia do Estado de Pernambuco(FACEPE)in Chile by Fondo Nacional de Desarrollo Científico y Tecnológico(FONDECYT)(Grant No.1210641)。
文摘The duality between electric and magnetic dipoles inspires recent comparisons between ferronics and magnonics.Here we predict surface polarization waves or“ferrons”in ferroelectric insulators,taking the long-range dipolar interaction into account.We predict properties that are strikingly different from the magnetic counterpart,i.e.the surface Damon-Eshbach magnons in ferromagnets.The dipolar interaction pushes the ferron branch with locked circular polarization and momentum to the ionic plasma frequency.The low-frequency modes are on the other hand in-plane polarized normal to their wave vectors.The strong anisotropy of the lower branch renders directional emissions of electric polarization and chiral near fields when activated by a focused laser beam,allowing optical routing in ferroelectric devices.
文摘In this work the neutral-current scattering cross-section for neutrinos on electrons is calculated assuming that a massive Dirac neutrino is characterized by a phenomenological parameters, a charge radius 2> and the right-handed currents are present in the framework of a Left-Right symmetric model (LR). Using the CHARM II result for the charge radius of the muon-neutrino |2>|<6.0×10-33cm2, we place a bound on -7.9×10-33cm2≤2>LR≤7.9×10-33cm2. We discuss the relationship between the electron neutral couplings gVeV and gVeA and the LR model parameters. We also estimate a bound on the heavy massive neutral vector boson mass MZR>650GeV of the LR model. These results have never been reported in the literature before and could have practical or theoretical interest, such as in the case of the neutrinos produced in core-collapse supernova explosions, that is to say, right-handed Dirac neutrinos emission from supernova core vLe-→vRe-.
基金supported under the grant CB0407the ICTP Office of External Activities through NET-35+3 种基金the fellowship CLAF-ICTPIGA-USP for the hospitalitysupport given by the International Center for Relativistic Astrophysics Networkthe financial support of the CNPq and FAPESP Agencies(Brazil)
文摘We revisit the problem of the maximum masses of magnetized white dwarfs （WDs）. The impact of a strong magnetic field on the structure equations is addressed. The pressures become anisotropic due to the presence of the magnetic field and split into parallel and perpendicular components. We first construct stable solutions of the Tolman-Oppenheimer-Volkoff equations for parallel pressures and find that physical solutions vanish for the perpendicular pressure whenB ≥ 10^13 G. This fact estab- lishes an upper bound for a magnetic field and the stability of the configurations in the （quasi） spherical approximation. Our findings also indicate that it is not possible to obtain stable magnetized WDs with super-Chandrasekhar masses because the val- ues of the magnetic field needed for them are higher than this bound. To proceed into the anisotropic regime, we can apply results for structure equations appropriate for a cylindrical metric with anisotropic pressures that were derived in our previous work. From the solutions of the structure equations in cylindrical symmetry we have con- firmed the same bound for B- 10^13 G, since beyond this value no physical solutions are possible. Our tentative conclusion is that massive WDs with masses well beyond the Chandrasekhar limit do not constitute stable solutions and should not exist.
基金support of the National Natural Science Foundation of China (NSFC, Grant No. 11390373)HXZ acknowledges support from the China Postdoctoral Science Foundation (Grant No. 2013M530008)+1 种基金the CAS-CONICYT Postdoctoral Fellowship, administered by the Chinese Academy of Sciences South America Center for Astronomy (CASSACA)MF acknowledges the NSFC (Grant No. 11203081)
文摘We investigated the evolutionary stages and disk properties of 211 young stellar objects（YSOs） across the Perseus cloud by modeling their broadband optical to mid-infrared（IR） spectral energy distribution（SED）. Our optical gri photometry data were obtained from the recently finished Purple Mountain Observatory Xuyi Schmidt Telescope Photometric Survey of the Galactic Anti-center（XSTPS-GAC）.About 81% of our sample fall into the Stage II phase which is characterized by having optically thick disks, while 14% into the Stage I phase characterized by having significant infalling envelopes, and the remaining 5% into the Stage Ⅲ phase characterized by having optically thin disks. The median stellar age and mass of the Perseus YSOs are 3.1 Myr and 0.3 M⊙ respectively. By exploring the relationships among the turnoff wave bands λturnoff（longward of which significant IR excesses above the stellar photosphere are observed）, the excess spectral index αexcess as determined for λ 〉 λturnoff, and the disk inner radius Rin（determined from SED modeling） for YSOs at different evolutionary stages, we found that the median and standard deviation of αexcess for YSOs with optically thick disks tend to increase withλturnoff, especially at λturnoff ≥5.8 μm, whereas the median fractional dust luminosities Ldust/L★ tend to decrease with increasing λturnoff. This points to an inside-out process of disk clearing for small dust grains. Moreover, a positive correlation between αexcess and Rin was found at α〉excess ～ 0 and R〉in～ 10 × the dust sublimation radius Rsub, irrespective of λturnoff, Ldust/L★ and disk flaring. This suggests that the outer disk flaring either does not evolve synchronously with the inside-out disk clearing of small dust grains or has little appreciable influence on the spectral slopes at λ〈～ 24 μm. About 23% of our YSO disks are classified as transitional disks, which haveλturnoff ≥ 5.8 μm and Ldust/L★ 〉 10-3. The transitional disks and full disks occupy distinctly different regions on the Ldust/L★ vs. αexcess diagram. Taking Ldust/L★ as an approximate discriminator of disks with（〉0.1） and without（〈0.1） considerable accretion activity, we found that 65% and 35% of the transitional disks may be consistent with being dominantly cleared by photoevaporation and dynamical interaction with giant planets respectively. None of our transitional disks have αexcess（〈0.0） or Ldust/L★（〉0.1） values that would otherwise be suggestive of disk clearing dominanted by grain growth.
文摘In the solution of the Klein-Gordon equation for the shutter problem, we prove that, at internuclear distances, a relativistic beam of Pi-mesons has a probability density which oscillates in time in a similar way to the spatial dependence in optical Fresnel diffraction from a straight edge. However, for an extreme-relativistic beam, the Fresnel oscillations turn into quantum damped beat oscillations. We prove that quantum beat oscillations are the consequence, at extreme-relativistic velocities, of the interference between the initial incident wave function, and the Green’s function in the relativistic shutter problem. This is a pure quantum relativistic phenomenon.
文摘Motivated by the recent result reported from LHC on the di-photon search from the Standard Model (SM) Higgs boson, we obtain limits on the anomalous couplings Hγγ and HZγ. We also perform a calculation at tree level of the decay widths as well as of the branching ratios for the reactions H → γγ and H → Zγ in the context of effective lagrangian for Higgs boson masses 115 ≤MH ≤ 130 GeV. We find that the decay widths and branching ratios from these reactions enhanced significantly due to the anomalous Hγγ and HZγ vertex, which would lead to measurable effects in Higgs signals at the LHC. Moreover, our results complement other studies on the channels H → γγ and H → Zγ.
文摘In this study,we investigated the anomalous Chromomagnetic Dipole Moment(CMDM),denoted as μ_(q)^(BLHM),of light quarks q=(u,c,d,s,b) within the framework of the Bestest Little Higgs Model(BLHM)as an extension of the Standard Model(SM).Our investigation encompassed novel interactions among the light quarks,heavy quark B,and heavy bosons (W'^(±),H^(±),φ^(±),η^(±))incorporating the extended Cabibbo-Kobayashi-Maskawa(CKM)matrix characteristic of the BLHM.We thoroughly explored the permissible parameter space,yielding a spectrum of CMDM values ranging from 10^(-10) to 10^(-3).
基金financially supported by the European Regional Development Fund through the Operational Competitiveness Program and the National Foundation for Science and Technology of Portugal(FCT)(No.UID/CTM/00264/2020 of Centre for Textile Science and Technology(2C2T)on its components Base and programmatic)support from project GreenAuto-Green Innovation for the Automotive Industry-PPS 3-Technical Textiles for the vehicle(Refa C6448637037-00000013)financed by EU funds,through the Plano de Recuperacao e Resiliência(PRR),managed by IAPMEI,I.P.-Agência para a Competitividade e Inovacao+2 种基金support within the scope of the project CICECO-Aveiro Institute of Materials,UIDB/50011/2020,UIDP/50011/2020&LA/P/0006/2020,financed by national funds through the FCT/MCTES(PIDDAC)support from the Spanish Ministry of Universities with European Union funds-Next Generation EU through a Margarita Salas fellowshipsupport received from National Science Foundation under PREM award DMR 2122178。
文摘The effect of temperature on the electrical conductivity(σ)and Seebeck coefficient(S)of n-type vapor grown carbon nanofibers(CNFs)and poly(vinylidene fluoride)(PVDF)melt-mixed with 15 wt%of those CNFs is analyzed.At 40°C,the CNFs show stable n-type character(S=-4.8μV·K^(-1))with anσof ca.165 S·m^(-1),while the PVDF/CNF composite film shows anσof ca.9 S·m^(-1)and near-zero S(S=-0.5μV·K^(-1)).This experimental reduction in S is studied by the density functional tight binding(DFTB)method revealing a contact electron transfer from the CNFs to the PVDF in the interface.Moreover,in the temperature range from 40°C to 100°C,theσ(T)of the CNFs and PVDF/CNF film,successfully described by the 3D variable range hopping(VRH)model,is explained as consequence of a thermally activated backscattering mechanism.On the contrary,the S(T)from 40°C to 100°C of the PVDF/CNF film,which satisfactorily matches the model proposed for some multi-walled carbon nanotube(MWCNT)doped mats;however,it does not follow the increase in S(T)found for CNFs.All these findings are presented with the aim of discerning the role of these n-type vapor grown carbon nanofibers on theσand S of their melt-mixed polymer composites.
文摘Ferroelectric ceramics are important materials with a wide range of industrial and commercial applications.Since the discovery of the phenomenon of ferroelectricity,they have been the heart and soul of several multibillion dollar industries,ranging from highdielectric-permittivity capacitors to developments in piezoelectric transducers,pyroelectric sensors,medical diagnostic transducers,electro-optical devices,etc.Materials based on barium titanate and lead zirconate titanate have dominated the field throughout their history.Actually,the ferroelectric ceramics from the Aurivillius family receive great attention due to their large remanent polarization,lead-free nature,relatively low processing temperatures,high Curie temperatures and excellent piezoelectric properties,which made them good candidates for multiple applications.This review presents a general overview of the progress in the studies on the ferroelectric ceramics from the Aurivillius family.The progress includes several aspects:(i)structural studies,(ii)dielectric and electric behavior,(iii)piezoelectricity,and(iv)pyroelectricity.
基金support provided by the CCADET-UNAM Schol-arship Programme
文摘In this work,we intend to perform a detailed study on the crystallization process of PZT 53/47 nanostructured powders by starting out with an amorphous precursor synthesized by a sol-gel based solution.Our interests also lie in the feasibility for controlling the average grain size of the final structure in the submicron range on an ab initio basis.Purposely,Fourier transform infrared spectroscopy（FT-IR）,Raman（Stokes and Anti-Stokes）,X-ray diffraction（XRD） and scanning electron microscopy（SEM） are used to examine the microstructural characteristics based on previously reported differential thermal analysis/thermal gravimetric analysis（DTA/TGA） data.The results show a crystallization temperature of 800℃ to attain pure perovskite phase with excellent morphological quality,average grain size 〈DG〉〈 300 nm and with average crystallite size 〈DC〉〈15 nm.
基金This research was supported by the Fundaçao de Amparo a Pesquisa do Estado de Sao Paulo—FAPESP(Project:2017/13769-1)Coordenaçao de Aperfeiçoamento de Pessoal de Nível Superior-CAPES(CAPES-PRINT Project:88881.310513/2018-01,88887.469068/2019-00 and 88887.508251/2020-00).
文摘BiFeO_(3)thin films were prepared using the chemical solution route on Pt/TiO_(2)/SiO_(2)/Si(100)substrates under different crystallization kinetics.The crystallization kinetic effects on the dielectric and electrical properties have been investigated.These properties included dielectric permittivity,electric modulus,electrical conductivity measurements as a function of the temperature(300-525 K)and frequency(10^(2)-10^(6)Hz),and leakage current measurements electric field range±30 kV/cm at room temperature.The differences observed in conductivity and current density of the BiFeO_(3)films were discussed in terms of possible defects induced by the crystallization kinetic.An anomalous relaxor-like dielectric behavior characterized by a broad maximum in the real dielectric permittivity as a function of temperature and the low-frequency dielectric dispersion has been observed.The nonexpected peaks in the real permittivity were accompanied by increasing at least four orders in the conductivity’s magnitude at high temperatures.The origin of the relaxor-like dielectric anomalies is discussed,suggesting that the dielectric permittivity peaks are artifacts due to carrier migration correlated to the onset of the Maxwell-Wagner effect.
