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研究了纳米晶Dy0 5 Sr0 5 CoO3 Y 的光谱特性 ,结果表明 :当晶粒尺寸减小至纳米量级时 ,发射光谱的激子峰波长蓝移 ;XRD ,FTIR谱表明 ,与体材料相比 ,纳米晶的衍射峰宽化 ,纳米晶的红外谱带大劈裂和宽化 ,表现为纳米尺寸量子化效应。 相似文献
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以EDTA为络合剂,聚乙二醇为有机分散剂,用络合溶胶-凝胶法制备出Gd_2O_3:Eu纳米晶。用XRD,SEM,X-射线能量色散谱仪(EDS),荧光分光光度计等分析手段对Gd_2O_3:Eu的纳米晶结构、形貌、组分的均匀性以及发光特性进行了研究。结果表明:EDTA-M凝胶仅在800℃焙烧即可得到颗粒细小、组分均匀、纯立方相的Gd_2O_3:Eu纳米晶,颗粒基本呈球形,粒径为30nm左右。对样品的激发光谱、发射光谱测定表明:Gd_2O_3:Eu纳米晶在269nm光激发下发红光,发射光谱谱峰在611nm,与体材料基本相同;激发光谱中电荷迁移带(CTB)明显红移,从体材料的255nm移至269nm,移动了约14nm;猝灭浓度从体材料的6%提高到8%。 相似文献
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Gd2O3:Eu纳米晶的制备及其光谱性质研究 总被引:5,自引:2,他引:3
以EDTA为络合剂,聚乙二醇为有机分散剂,用络合溶胶—凝胶法制备出Gd2O3:Eu纳米晶。用XRD,SEM,X—射线能量色散谱仪(EDS),荧光分光光度计等分析手段对Gd2O3:Eu的纳米晶结构、形貌、组分的均匀性以及发光特性进行了研究。结果表明:EDTA—M凝胶仅在800℃焙烧即可得到颗粒细小、组分均匀、纯立方相的Gd2O3:Eu纳米晶,颗粒基本呈球形,粒径为30nm左右。对样品的激发光谱、发射光谱测定表明:Gd2O3:Eu纳米晶在269nm光激发下发红光,发射光谱谱峰在611nm,与体材料基本相同;激发光谱中电荷迁移带(CTB)明显红移,从体材料的255nm移至269nm,移动了约14nm;猝灭浓度从体材料的6%提高到8%。 相似文献
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ZnO:Eu3+纳米晶的制备及发光性质研究 总被引:4,自引:0,他引:4
为了探讨稀土Eu3 与纳米ZnO基质之间的能量传递,利用溶胶-凝胶法(Sol-Cel)制备了ZnO:Eu3 纳米晶,测量了样品的X射线衍射谱(XRD)、光致发光谱(PL)和激发谱(PLE).X射线衍射结果表明,ZnO:Eu3 具有六角纤锌矿晶体结构.观察到稀土Eu3 强而窄的特征发射和ZnO基质弱而宽的可见发射.分析了稀土Eu3 激发态5D0→7F1,5D0→7F3和5D0→7F2特征发射机制.给出了Eu3 离子特征发射的峰值强度随掺Eu3 浓度增加而增强的变化关系,证实了纳米ZnO基质与稀土Eu3 离子之间存在能量传递.比较了Eu3 离子5D0→7Fl磁偶极跃迁(MD)与5D0→7F2电偶极跃迁(ED)的相对强度,证实了在ZnO纳米晶基质中大多数Eu3 占据了对称性较低的格位. 相似文献
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Co3O4纳米晶的制备和表征 总被引:3,自引:0,他引:3
发现了一种新制备Co3O4纳米晶的新方法。这种方法是先将高分子聚乙烯吡咯烷酮(PVP)和乙酸钴溶解到溶剂中缓慢蒸发溶剂,然后干燥形成的前驱体,最后在400℃温度下煅烧制备了Co3O4纳米晶。生成的产物用XRD,SEM,TEM等测试方法进行了表征。结果发现在不同的溶剂中形成前驱体所制备的Co3O4纳米晶具有不同的形貌特征,使用乙醇溶剂时生成了大量的由Co3O4纳米晶自组装形成的Co3O4微米球;而使用水溶剂时则生成的全都是Co3O4纳米晶。实验结果表明在不同溶剂中形成的前驱体对于最终制备的Co3O4纳米晶形态有着很大的影响。 相似文献
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采用柠檬酸作燃烧剂用燃烧合成法制备了Gd2O3:Eu3+纳米晶.用X射线衍射仪(XRD)、高分辨透射电子显微镜(HRTEM)和荧光分光光度计等对Gd2O3:Eu3+纳米晶的结构、形貌和发光性能进行了分析.结果表明:不同柠檬酸与稀土离子配比(C/M)制备的样品经800℃退火1 h后,均得到了纯立方相的Gd2O3:Eu3+纳米晶,晶粒尺寸约为30 nm,尺寸分布较窄,其中以C/M=1.0时制备的纳米晶结晶性最好,发光强度最大.Gd2O3:Eu3+纳米晶主发射峰位置均在612 nm处(5D0→7F2跃迁),激发光谱中电荷迁移态发生红移,观察到Gd3+向Eu3+的有效能量传递.对柠檬酸与稀土离子配比(C/M)对结晶度、发光性质等的影响也进行了分析和讨论. 相似文献
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利用高温热分解法制备了LiLuF_4∶Yb,Tm@LiGdF_4核壳纳米晶。在980nm激光激发下,与未包覆的样品相比,LiLuF_4∶Yb,Tm@LiGdF_4核壳纳米晶的发光增强了15倍左右,这主要是因为通过惰性壳层的包覆可以有效抑制表面猝灭效应。另外,随着核中Yb~(3+)离子的摩尔分数从20%增加到100%,上转换发光强度逐渐增大,最大增加了12.4倍左右。这主要是由于增加Yb~(3+)离子的浓度可以增加纳米粒子对激发光的吸收和提高Yb~(3+)到Tm~(3+)的能量传递速率。所制备的LiYbF_4∶2%Tm@LiGdF_4核壳纳米晶的发光效率高达4%。 相似文献
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本文针对Sm3Co粗晶和纳米晶合金材料的制备和基础性能进行了研究.采用磁悬浮熔炼技术多次精炼制备出Sm3Co粗晶合金.以此为母材,利用高能球磨非晶化和放电等离子烧结致密化并同步晶化的技术路线,制备出平均晶粒尺寸为8 nm的超细纳米晶Sm3Co合金块体材料.构建了Sm3Co纳米晶合金的晶体结构模型,并结合其显微组织的表征,分析了Sm3Co纳米晶合金的磁性能和力学性能,并与粗晶合金进行了比较粗晶Sm3Co合金不具有硬磁特性,而同种成分的纳米晶合金则表现出一定的硬磁特性.纳米晶Sm3Co合金的显微硬度和弹性模量分别达到4.87 GPa和63.7 GPa,比粗晶合金增大约8.7%和13.3%.本文研究结果为Sm-Co体系合金的基础性能及其纳米尺度效应提供了系统的参考依据. 相似文献
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利用磁控溅射和Sr成分的调制以及原位热处理方法,在10mm×10mm大小的(001) 取向SrTiO3单晶衬底上制备出三明治结构为La0.7Sr0.3MnO3(100nm)/La0.96Sr0.04MnO3 (5nm)/ La0.7Sr0.3MnO3 (100nm) 的隧道结外延薄膜,然后再次 利用磁控溅射方法,在三层单晶膜上方继续沉积Ir22Mn78(15n m)/Ni79Fe21(5nm)/Pt(20nm)等金属三层膜.最后利用深紫外曝 光和Ar离子束刻蚀等微加工技术,制备出长短轴分别为12和6μm或者8和4μm大小的椭圆形L a1-xSrxMnO3成分调制的复合磁性隧道结.在4.2K和 外加磁场8 T的测试下,La1-xSrxMnO3成分调制的复 合磁性隧道结其隧穿磁电阻(TMR)比值达到3270%, 直接从实验上证实了铁磁性La0.7 sub>Sr0.3MnO3金属氧化物的自旋极化率(97%)可接近100%,具 有很好的半金属性质.
关键词:
1-xSrxMnO3')" href="#">La1-xSrxMnO3
半金属
成分调制
复合磁性隧道 结
隧穿磁电阻 相似文献
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《中国物理快报》2021,(8)
Interface engineering is an effective and feasible method to regulate the magnetic anisotropy of films by altering interfacial states between films.Using the technique of pulsed laser deposition,we prepared La_(0.67)Sr_(0.33)MnO_3(LSMO) and La_(0.67)Sr_(0.33)MnO_3/SrCoO_(2.5)(LSMO/SCO) films on(110)-oriented La_(0.3)Sr_(0.7)Al_(0.65)Ta_(0.35)O_3 substrates.By covering the SCO film above the LSMO film,we transformed the easy magnetization axis of LSMO from the [001] axis to the [110] axis in the film plane.Based on statistical analyses,we find that the corresponding Mn-Mn ionic distances are different in the two types of LSMO films,causing different distortions of Mn-O octahedron in LSMO.In addition,it also induces diverse electronic occupation states in Mn~(3+) ions.The eg electron of Mn~(3+)occupies 3 z~2-r~2 and x~2-y~2 orbitals in the LSMO and LSMO/SCO,respectively.We conclude that the electronic spin reorientation leads to the transformation of the easy magnetization axis in the LSMO films. 相似文献
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Effect of Terraces at the Interface on the Structural and Physical Properties of La_(0.8)Sr_(0.2)MnO_3 Thin Films 下载免费PDF全文
《中国物理快报》2016,(7)
Employing atomic force microscopy,transmission electron microscopy and the second harmonic generation technique,we carefully explore the structural properties of 6-unit-cell-thick La_(0.8)Sr_(0.2)MnO_3 films grown on SrTiO_3 with atomically flat TiO_2-terminated terraces on the surface.The results clearly demonstrate that the terraces on the surface of TiO_2-terminated SrTiO_3 can improve the layer-by-layer epitaxial growth of the manganite films,which results in uniform film coverage at the beginning of growth and thus reduces the substrate-induced disorder at or near the interface.Comparing the magnetic and transport properties of La_(0.8)Sr_(0.2)MnO_3 films with the thicknesses varying from 6 unit cells to 80 unit cells grown respectively on as-received SrTiO_3 and TiO_2-terminated SrTiO_3,it is found that these atomically flat terraces on the surface of TiO_2-terminated SrTiO_3 can greatly enhance the Curie temperature and conductivities of the ultrathin La_(0.8)Sr_(0.2)MnO_3 films with thickness less than 50 unit cells,while no obvious difference is detected in the magnetic and transport properties of the 80unit-cell thick films. 相似文献
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固相反应方法制得的La0.7Ca0.3MnO3 (LCMO)粉末与Ce O2粉末均匀混合后压块烧结,对其进行了电阻率随温度变化的测量.观察到样品电阻率存在绝缘体-金属转变. 研究了烧结工艺、CeO2的混合比例与样品的电阻率、结构和表面形貌的关系.结 果表明, 制备工艺对材料性能有相当大的影响,其中较低温度的烧结主要影响小晶粒及其晶粒间界, 而高温长时间烧结将影响大晶粒的形成.利用三维随机电阻网络(RRN)模型和蒙特卡罗方法 对这种混合块状样品的输运性质进行了模拟,模拟中使用了一种新的RRN平均方法.该模型得 到的数值模拟结果与实验结果在定性上是一致的.这说明以RRN模型来理解LCMO(x)-CeO 2(1-x) 复合体系的导电状况是合理的,提出的随机电阻网络平均方法是合适的 .
关键词:
0.7Ca0.3MnO3')" href="#">La0.7Ca0.3MnO3
绝缘体-金属转变
随 机电阻网络
蒙特卡罗模拟 相似文献
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Strain Induced Nanopillars and Variation of Magnetic Properties in La_(0.825)Sr_(0.175)MnO_3/LaAlO_3 Films 下载免费PDF全文
To investigate the process of strain relaxation and resultant variation of microstructure and magnetic properties,low-doped La_(0.825)Sr_(0.175)MnO_3 epitaxial films with different thicknesses are deposited on LaAlO_3 substrates and strain induced nanopillars are discovered inside the La_(0.825) Sr_(0.175)MnO_3 film. Perpendicular oriented nanopillars mainly exist below 30 nm and tend to disappear above 30 nm. The distribution of nanopillars not only induce the variation of lattice parameters and local structural distortion but also lead to the deviation of easy magnetization axis from the perpendicular direction. Specifically, the out-of-plane lattice parameters of the film decrease quickly with the increase of the thickness but tend to be constant when the thickness is above 30 nm. Meanwhile, the variations of magnetic properties along in-plane and out-of-plane directions would also decline at first and they then remain nearly unchanged. Our work constructs the relationship between nanopillars and magnetic properties inside films. We are able to clearly reveal the effects of inhomogeneous strain relaxation. 相似文献
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用化学镀法制备了铜包覆的La_(0.7)Ca_(0.3)MnO_3(LCMO)颗粒.这些粉末压片之后在氩气中煅烧,形成铁磁-金属型结构,得到被铜均匀包覆的LCMO复合材料.利用扫描电子显微镜(SEM)观察了LCMO被铜包覆的形貌.研究了不同烧结温度下样品的电输运性质和在0.3T外加磁场下的磁电阻行为.结果表明LCMO在通过包覆铜进行表面修饰后,样品的绝缘体-金属的转变温度(Tp)往高温移动接近室温,室温附近的磁电阻值也得到显著提高. 相似文献
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Emergent ferroelectricity in disordered tri-color multilayer structure comprised of ferromagnetic manganites 下载免费PDF全文
Multiferroic materials,showing the coexistence and coupling of ferroelectric and magnetic orders,are of great technological and fundamental importance.However,the limitation of single phase multiferroics with robust magnetization and polarization hinders the magnetoelectric effect from being applied practically.Magnetic frustration,which can induce ferroelectricity,gives rise to multiferroic behavior.In this paper,we attempt to construct an artificial magnetically frustrated structure comprised of manganites to induce ferroelectricity.A disordered stacking of manganites is expected to result in frustration at interfaces.We report here that a tri-color multilayer structure comprised of non-ferroelectric La_(0.9)Ca_(0.1)MnO_3(A)/Pr_(0.85)Ca_(0.15)MnO_3(B)/Pr_(0.85)Sr_(0.15)MnO_3(C) layers with the disordered arrangement of ABC-ACBCAB-CBA-BAC-BCA is prepared to form magnetoelectric multiferroics.The multilayer film exhibits evidence of ferroelectricity at room temperature,thus presenting a candidate for multiferroics. 相似文献
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文章作者制备了以多种π-共轭有机半导体(orgnanic semincondutor,简称OSEC)为中间层,La2/3Sr1/3MnO3(LSMO)和另一铁磁或非磁性金属为电极的有机二极管,测量了器件的磁致电阻和磁电致发光效应.器件显示了与LSMO电极类似的负磁电阻效应,但是它的电阻变化比LSMO电极本身的变化大3个数量级,而且器件还有正的磁电致发光效应.文章作者认为,这些磁场效应源于磁场作用下LSMO费米能级的异常移动,导致载流子在LSMO-OSEC界面注入的增强。 相似文献
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《中国科学:物理学 力学 天文学(英文版)》2017,(4)
The ultrafast laser-excited magnetization dynamics of ferromagnetic(FM) La_(0.67)Sr_(0.33)MnO_3(LSMO) thin films with BiFeO_3(BFO) coating layers grown by laser molecular beam epitaxy are investigated using the optical pump-probe technique.Uniform magnetization precessions are observed in the films under an applied external magnetic field by measuring the time-resolved magneto-optical Kerr effect.The magnetization precession frequencies of the LSMO thin films with the BFO coating layers are lower than those of uncoated LSMO films,which is attributed to the suppression of the anisotropy field induced by the exchange interaction at the interface between the antiferromagnetic order of BFO and the FM order of LSMO. 相似文献