Y3MnxFe4.85–xO12 （x=0, 0.02, 0.04, 0.06, 0.08 and 0.1） garnet ferrites （YMnIG） were prepared by conventional solid-state reaction method in air atmosphere. The effect of Mn addition on the microstructure and elec...Y3MnxFe4.85–xO12 （x=0, 0.02, 0.04, 0.06, 0.08 and 0.1） garnet ferrites （YMnIG） were prepared by conventional solid-state reaction method in air atmosphere. The effect of Mn addition on the microstructure and electromagnetic properties of YIG were investigated by means of techniques such as X-ray diffraction, scanning electron microscopey, network analyzer, hysteresigraph, magnetic balance and electron paramagnetic resonance spectrometry. Pure garnet phase of Y3Fe5O12 was identified for all the samples, except for minor YFeO3 phase appearing in the sample with x=0.06. The addition of Mn showed little influence on the dielectric constant of YIG, which varied between 14.2 and 14.5. Substituting Mnn＋ for Fen＋ in YIG decreased the total amount of Fe ions, inhibited the reduction of Fe3＋ and promoted the grain growth of garnet phase, which led to the decrease in dielectric loss and coercivity. Because the amount of Mn3＋ ions in octahedral sites in- creased with Mn concentration, the saturation magnetization showed a slight decrease firstly and then increased notably. The addition of Mn could also increase the remanence ratio of YIG ferrites by decreasing the magnetostriction constant λ111. Therefore, doping Mn into YIG fer- rites with proper quantity could improve electromagnetic properties of YIG significantly. The YMnIG ferrite with x=0.08, i.e., Y3Mn0.08 Fe4.77O12, showed the optimum electromagnetic properties： εr=14.2, tanδe=1.5×10–4, Hc=36 A/m, 4πMS=192 mT, Br/Bs=0.84, ？H=6.8 KA/m.展开更多
In this paper, a novel approach is presented to synthesize microwave medium of negative refractive index by incorporating metallic wire array with negative effective permittivity into the host media such as ferrimagne...In this paper, a novel approach is presented to synthesize microwave medium of negative refractive index by incorporating metallic wire array with negative effective permittivity into the host media such as ferrimagnet-YIG (yttrium iron garnet) applied by external magnetic field whose permeability is negative. We have designed the composite medium having negative refractive index in C/X band frequencies, analyzed and simulated its electromagnetic (EM) properties by use of EM EDA package based on time-domain finite integration method. The simulation results show that: ① the effective permittivity of the designed metallic wire array is negative in the frequency range from 7.02 GHz to 9.80 GHz; ② the permeability of YIG substrate immersed into an external magnetic field is negative in the frequency range from 5.22 GHz to 8.14 GHz; ③ EM wave can pass through the composite medium synthesized by the above designed metallic wire array and YIG substrate, and ④ the negative refraction behavior occurs on the interface between the composite medium and the normal material with positive refractive index in 7.51―8.13 GHz frequency range, in which the effective permittivity of the metallic wire array and the permeability of YIG substrate are negative simultaneously. The full wave simulation has demonstrated that the effective refractive index of the designed composite medium is indeed negative and ascertained that the proposed approach to design microwave medium with negative refractive index is viable.展开更多
Yttrium iron garnet(YIG)is a promising material for various terahertz applications due to its special optical properties.At present,a high-quality YIG wafer is the desire of terahertz communities and it is still chall...Yttrium iron garnet(YIG)is a promising material for various terahertz applications due to its special optical properties.At present,a high-quality YIG wafer is the desire of terahertz communities and it is still challenging to prepare substrate-free YIG single crystal films.In this work,we prepared wafer-level substrate-free La:YIG single crystal films,for the first time,to our knowledge.Terahertz optical and magneto-optical properties of La:YIG films were characterized by terahertz time domain spectroscopy(THz-TDS).Results show that the as-prepared La:YIG film has an insertion loss of less than 3 dB and a low absorption coefficient of less than10 cm-1below 1.6 THz.Benefitting from the thickness of the substrate-free YIG films and low insertion loss,their terahertz properties could be further manipulated by simply using a wafer-stacking technique.When four La:YIG films were stacked,there was an insertion loss of less than 10 dB in the range of 0.1-1.2 THz.The Faraday rotation angle of the four-layer-stacked La:YIG films reached 19°,and the isolation could reach17 dB.By further increasing the stacking number to eight pieces,a remarkable Faraday rotation angle of45°was achieved with an isolation of 23 dB,which is important for practical application in the THz band.This material may provide a milestone opportunity to make various non-reciprocal devices,such as isolators and phase shifters.展开更多
Ce:YIG thin films are taken as an ideal candidate for magneto-optical devices with giant Faraday effect in the near-infrared range,but it is hindered by a limited Ce^(3+)/Ce^(4+)ratio and a high saturation driving fie...Ce:YIG thin films are taken as an ideal candidate for magneto-optical devices with giant Faraday effect in the near-infrared range,but it is hindered by a limited Ce^(3+)/Ce^(4+)ratio and a high saturation driving field.To address this issue,Eu doping can increase the Faraday rotation angle by ~40% to 1.315×10^(4)deg/cm and decrease the saturation driving field by ~38%to 1.17 kOe in Eu_(0.75)Ce_(1)Y_(1.25)Fe_(5)O_(12 )compared to Ce_(1)Y_(2)Fe_(5)O_(12)pristine.The mechanism is attributed to the conversion of Ce^(4+)to Ce^(3+)and the weakening of ferrimagnetism by Eu doping.This work not only provides strategies for improving Ce^(3+)/Ce^(4+) ratio in Ce:YIG,but also develops(Eu,Ce):YIG with a promising Faraday rotation angle for magneto-optical devices.展开更多
基金Project supported by the State Commission of Science and Technology for National Defense Industry
文摘Y3MnxFe4.85–xO12 （x=0, 0.02, 0.04, 0.06, 0.08 and 0.1） garnet ferrites （YMnIG） were prepared by conventional solid-state reaction method in air atmosphere. The effect of Mn addition on the microstructure and electromagnetic properties of YIG were investigated by means of techniques such as X-ray diffraction, scanning electron microscopey, network analyzer, hysteresigraph, magnetic balance and electron paramagnetic resonance spectrometry. Pure garnet phase of Y3Fe5O12 was identified for all the samples, except for minor YFeO3 phase appearing in the sample with x=0.06. The addition of Mn showed little influence on the dielectric constant of YIG, which varied between 14.2 and 14.5. Substituting Mnn＋ for Fen＋ in YIG decreased the total amount of Fe ions, inhibited the reduction of Fe3＋ and promoted the grain growth of garnet phase, which led to the decrease in dielectric loss and coercivity. Because the amount of Mn3＋ ions in octahedral sites in- creased with Mn concentration, the saturation magnetization showed a slight decrease firstly and then increased notably. The addition of Mn could also increase the remanence ratio of YIG ferrites by decreasing the magnetostriction constant λ111. Therefore, doping Mn into YIG fer- rites with proper quantity could improve electromagnetic properties of YIG significantly. The YMnIG ferrite with x=0.08, i.e., Y3Mn0.08 Fe4.77O12, showed the optimum electromagnetic properties： εr=14.2, tanδe=1.5×10–4, Hc=36 A/m, 4πMS=192 mT, Br/Bs=0.84, ？H=6.8 KA/m.
基金Supported by the National Natural Science Foundation of China (Grant No. 60571024) Key Science and Technology Foundation for Youth of UESTC (Grant No. JX04001)
文摘In this paper, a novel approach is presented to synthesize microwave medium of negative refractive index by incorporating metallic wire array with negative effective permittivity into the host media such as ferrimagnet-YIG (yttrium iron garnet) applied by external magnetic field whose permeability is negative. We have designed the composite medium having negative refractive index in C/X band frequencies, analyzed and simulated its electromagnetic (EM) properties by use of EM EDA package based on time-domain finite integration method. The simulation results show that: ① the effective permittivity of the designed metallic wire array is negative in the frequency range from 7.02 GHz to 9.80 GHz; ② the permeability of YIG substrate immersed into an external magnetic field is negative in the frequency range from 5.22 GHz to 8.14 GHz; ③ EM wave can pass through the composite medium synthesized by the above designed metallic wire array and YIG substrate, and ④ the negative refraction behavior occurs on the interface between the composite medium and the normal material with positive refractive index in 7.51―8.13 GHz frequency range, in which the effective permittivity of the metallic wire array and the permeability of YIG substrate are negative simultaneously. The full wave simulation has demonstrated that the effective refractive index of the designed composite medium is indeed negative and ascertained that the proposed approach to design microwave medium with negative refractive index is viable.
基金National Key Research and Development Program of China(2023YFB3811300,2023YFB3811305)National Natural Science Foundation of China(62235004,61831012,62371258,62311530115)+1 种基金Sichuan Province Science and Technology Support Program(2021JDTD0026,2023JDGD0012)Shenzhen Science and Technology Program((2021)105)。
文摘Yttrium iron garnet(YIG)is a promising material for various terahertz applications due to its special optical properties.At present,a high-quality YIG wafer is the desire of terahertz communities and it is still challenging to prepare substrate-free YIG single crystal films.In this work,we prepared wafer-level substrate-free La:YIG single crystal films,for the first time,to our knowledge.Terahertz optical and magneto-optical properties of La:YIG films were characterized by terahertz time domain spectroscopy(THz-TDS).Results show that the as-prepared La:YIG film has an insertion loss of less than 3 dB and a low absorption coefficient of less than10 cm-1below 1.6 THz.Benefitting from the thickness of the substrate-free YIG films and low insertion loss,their terahertz properties could be further manipulated by simply using a wafer-stacking technique.When four La:YIG films were stacked,there was an insertion loss of less than 10 dB in the range of 0.1-1.2 THz.The Faraday rotation angle of the four-layer-stacked La:YIG films reached 19°,and the isolation could reach17 dB.By further increasing the stacking number to eight pieces,a remarkable Faraday rotation angle of45°was achieved with an isolation of 23 dB,which is important for practical application in the THz band.This material may provide a milestone opportunity to make various non-reciprocal devices,such as isolators and phase shifters.
基金supported by the National Science Fund for Distinguished Young Scholars (Grant No. 52225201)the National Natural Science Foundation of China (Grant Nos. 52072085 and 52271207)+3 种基金the National Key Research and Development Program of China (Grant No. 2023YFE0201000)the Fundamental Research Funds for the Central Universities (Grant No. HIT.BRET.2022001)the Heilongjiang Touyan Innovation Team Programthe Science Foundation of National Key Laboratory of Science and Technology on Advanced Composites in Special Environments。
文摘Ce:YIG thin films are taken as an ideal candidate for magneto-optical devices with giant Faraday effect in the near-infrared range,but it is hindered by a limited Ce^(3+)/Ce^(4+)ratio and a high saturation driving field.To address this issue,Eu doping can increase the Faraday rotation angle by ~40% to 1.315×10^(4)deg/cm and decrease the saturation driving field by ~38%to 1.17 kOe in Eu_(0.75)Ce_(1)Y_(1.25)Fe_(5)O_(12 )compared to Ce_(1)Y_(2)Fe_(5)O_(12)pristine.The mechanism is attributed to the conversion of Ce^(4+)to Ce^(3+)and the weakening of ferrimagnetism by Eu doping.This work not only provides strategies for improving Ce^(3+)/Ce^(4+) ratio in Ce:YIG,but also develops(Eu,Ce):YIG with a promising Faraday rotation angle for magneto-optical devices.
