共查询到18条相似文献,搜索用时 187 毫秒
1.
给出了采用平行泵激励方式,纯YIG和多种掺Gd石榴石结构微波铁氧体材料在脉冲宽度t_d分别为0.7、1.0、1.5和2.0μs时,临阈射频场h_(ct)的测量结果,通过外推计算出这些材料无限宽脉冲下的自旋波线宽ΔH_k。结果表明,微波铁氧体材料的高功率承受能力不仅与材料的自旋波线宽ΔH_k有关,还与h_(ct)外推直线的斜率及所在高功率微波信号的脉冲宽度t_d有密切的关系;在工程应用中,选择高功率微波铁氧体材料除了需考虑材料的自旋波线宽ΔH_k,还应充分了解材料在不同脉冲宽度下的临阈射频场h_(ct)。 相似文献
2.
通过减低各向异性磁场和气孔率,可使锡钙钒系多晶石榴石的铁磁共振线宽(ΔH)降低到2奥以下。为了在实验中弄清这种多晶的最终损耗机理,作者在8~460μm的范围内,变动多晶体晶粒的平均颗粒尺寸(a_o),测量其线宽的频率特性,从而分离出与晶粒尺寸有依赖关系的损耗项((ΔH)a_o有关)。结果发现损耗项(ΔH)a_o有关)按照共振频率(ω_o)在自旋波簇之内、上限和之外等不同情况而分别与a_o~(-0.2)、a_o~(-0.6)、a_o~(-1)成比例。为了研究此类铁氧体的固有损耗,对于a_o=460μm的样品测量了ω_o在簇外时的ΔH,所得值为0.3奥。该值是迄今测得的多晶铁氧体的ΔH值中最小的值。 相似文献
3.
采用陶瓷工艺制备了Ni_(1-z)Co_z Fe_2O_4(0≤z≤0.04)微波铁氧体材料,研究了快弛豫离子Co~(2+)取代对Ni铁氧体材料微波性能的影响。结果表明,加入微量取代离子Co~(2+),随取代量的增大铁氧体材料的自旋波线宽ΔHk呈线性增大;材料的铁磁共振线宽ΔH先降后升,在Co含量为z=0.02时,材料ΔH出现最小值;Co~(2+)取代对材料的饱和磁化强度M_s、介电损耗的影响不大。 相似文献
4.
《磁性材料及器件》2020,(2)
采用普通陶瓷工艺制备Bi_xCa_(a+2b)Y_(3–x–(a+2b))Zr_aV_bFe_(5–a–b)O_(12)(x=1.2,1.4,1.5,1.6)多晶石榴石铁氧体材料,研究了Bi~(3+)取代对材料显微结构、介电常数e'及饱和磁化强度、铁磁共振线宽等磁性能的影响。研究表明,随着Bi~(3+)取代量增加,材料饱和磁化强度降低,密度和介电常数ε'均增高,而铁磁共振线宽ΔH显著增大。当Bi~(3+)取代量x=1.4时,介电常数超过30,x=1.6时,ε'达到35以上,比普通石榴石的e'高出20,大幅提升了材料的介电常数,但却因其ΔH高达9 k A/m(113 Oe)不具应用价值。 相似文献
5.
利用热压工艺制备出了细晶粒(2μm)YIG铁氧体材料,测量了其微波性能,结果表明,细晶粒铁氧体的自旋波线宽ΔHk显著提高,其ΔHk与晶粒尺寸有a0^-1.7的相依关系。同时,分析讨论了细晶粒铁氧体铁磁共振线宽ΔH的致宽因素。 相似文献
6.
一、前言钇钆铁石榴石(YGdIG),是一种通用微波铁氧体材料,微波器件的插入损耗与它的铁磁共振线宽△H 有关,要降低△H 必需使成分尽可能地接近于正分。在 相似文献
7.
采用普通陶瓷工艺制备了饱和磁化强度Ms为80~148 kA/m的小线宽石榴石铁氧体材料,按GB/T9633(等同IEC60556)标准)在10.7 GHz下测量了复合石榴石铁氧体的介电常数ε′和介电损耗角正切tanδ_ε。研究了e'与材料密度、饱和磁化强度Ms和缺铁量的关系。实验表明,e'随密度的增加而增大,随Ms的下降而减小,随缺铁量增加而降低。即,介电常数随着配方中代换离子的增加、Fe含量的减少而下降,说明了e'与Fe浓度密切相关。 相似文献
8.
采用普通陶瓷工艺制备了Sn4+取代的Ni系尖晶石Ni1-a+xCuaSnxMnbFe2-b-2xO4微波多晶铁氧体材料,研究了材料性能随Sn4+取代量的变化。结果表明,铁磁共振线宽ΔH随Sn4+取代量x的增大先减小后增大,当x=0.1时,ΔH有最小值;饱和磁化强度Ms、居里温度TC随取代量x的增大单调降低,在x=0.1时不存在拐点。初步分析了各向异性线宽ΔHa和气孔致宽ΔHp对ΔH的贡献,得出ΔH先降低而后增大是由各向异性线宽ΔHa所致。 相似文献
9.
用标准的陶瓷工艺制备了成分为Ca_(3-y)Bi_yFe_(3.5-0.5x+0.5y)Ge_xV_(1.5-0.5x-0.5y)O_(12)的无钇多晶石榴石。能够获得这样的材料,它的居里点T(?)比掺铝的YIG的高,而4πM_s(≤800G)和ΔH值则相同。掺Ge~(4+)离子降低了材料的空孔率(0≤x≤0.3),而且降低了各向异性常数K_1(x≥0.5),这是因为一部分Ge~(4+)离子进入了石榴石结构的16a位置。根据自旋波理论,利用观测得到的单晶K_1/M_s;当0≤x≤0.3时,仅仅石榴石的全线宽的25%是由于各向异性增宽。米用适当的热压工艺,空孔率可降低到接近于零。当成分为(x=0.3,y=0.2)和(X=0.5,y=0.2)时获得了线宽分别为ΔH=12Oe和ΔH=6Oe的小线宽材料。 相似文献
10.
11.
用普通陶瓷工艺制备YIGs、YGdIGs和BiCaVIGs等系列石榴石多晶铁氧体,按GB9633(等同IEC60556)标准在10.7GHz下测量了复合石榴石YIGs、YGdIGs和BiCaVIGs的介电常数ε′和介电损耗角正切tanδε,同时也测量了9.37GHz下的铁磁共振线宽DH。比较了加与不加稳恒磁场时ε′和tanδε的测量结果,讨论了加磁场后介电损耗的下降。此外还研究了tanδε和DH与缺铁量的关系,分析了DH最小值对应的缺铁量和tanδε最小值对应的缺铁量不重合的原因。 相似文献
12.
Yen-Pei Fu Cheng-Hsiung Lin Kok-Wan Tay Yeong-Der Yao 《Journal of Electroceramics》2008,21(1-4):677-680
Yttrium iron garnet (YIG) nano-powders were successfully synthesized by microwave-induced combustion process. The as-prepared YIG powders were annealed at different temperature and investigated by XRD, SEM, and VSM. The as-received YIG powder shows the formation of garnet structure with saturation magnetization (M s) of 12 emu/g, whereas upon annealing at 825 °C for 2 h, the saturation magnetization increases to 27 emu/g. The as-received yttrium iron garnet powders annealed at several temperatures revealed that the particle size ranged from 65 to 90 nm. Moreover, the linewidth of magnetic resonance peak (ΔH), complex permeability, and loss tangent of sintered YIG ceramic are also examined in this study. 相似文献
13.
14.
15.
16.
Kimoto T. Kurobe T. Muranushi K. Mukaihara T. Kasukawa A. 《IEEE journal of selected topics in quantum electronics》2005,11(5):919-923
The effect of optical feedback from various reflected points on the spectral-linewidth was analyzed for a wavelength selectable laser consisting of a 12 distributed feedback (DFB) laser array, multimode interference coupler, and semiconductor optical amplifiers (SOA). For all 12 DFB lasers, a narrow linewidth of less than 2 MHz was achieved with over 50 mW by reducing facet reflectivity. 相似文献
17.
《IEEE journal of selected topics in quantum electronics》2009,15(3):514-520
18.
Le Qiu Larson T.A. Smith D.K. Vitkin E. Songhua Zhang Modell M.D. Itzkan I. Hanlon E.B. Korgel B.A. Sokolov K.V. Perelman L.T. 《IEEE journal of selected topics in quantum electronics》2007,13(6):1730-1738
Gold nanorods have the potential to be employed as extremely bright molecular marker labels for fluorescence, absorption, or scattering imaging of living tissue. However, samples containing a large number of gold nanorods usually exhibit relatively wide spectral lines. This linewidth limits the use of the nanorods as effective molecular labels, since it would be rather difficult to image several types of nanorod markers simultaneously. In addition, the observed linewidth does not agree well with theoretical calculations, which predict significantly narrower absorption and scattering lines. The discrepancy could be explained by apparent broadening because of the contribution of nanorods with various sizes and aspect ratios. We measured native scattering spectra of single gold nanorods with the confocal light absorption and scattering spectroscopy system, and found that single gold nanorods have a narrow spectrum as predicted by the theory, which suggests that nanorod-based molecular markers with controlled narrow aspect ratios, and to a lesser degree size distributions, should provide spectral lines sufficiently narrow for effective biomedical imaging. 相似文献