晶场二级效应与交换作用对PrF3晶体磁性及磁光性质的影响

研究了晶场二级效应在PrF₃晶体中的作用，发现该效应可使Pr³⁺离子的晶场单态与其他态混合，对PrF₃晶体磁化率产生明显影响.进一步研究了晶体内的交换作用有效场，其形式为H_in=(1.9-0.02556T)×10^-5M，在100—300 K的温度范围内，以此计算的PrF₃晶体的倒数磁化率和Verdet常数的倒数与实验值符合较好.结果表明，在PrF₃晶体中，晶场二级效应与离子间的交换作用都不能忽略. 关键词： 晶场二级效应 交换作用有效场 Verdet常数 3晶体')" href="#">PrF₃晶体     

Pr:YIG晶体抗磁性Faraday转动谱的研究

在单电子模型下，用量子理论研究了Pr:YIG晶体中Pr3+离子的抗磁性Faraday转动（FR）谱.分别在温度为77K和300K时，计算了Pr3+离子的λF-1/2θ-λ2的变化关系，计算结果与实验值符合较好.证实了晶场为单态的离子，其抗磁性FR比顺磁性FR对交换场（或外场）有更大的依赖性，且与温度有关.在强交换场环境中，两种转动对FR的贡献有相同的重要性. 关键词： Pr:YIG晶体 单离子模型 抗磁性Faraday转动     

PrNi$lt;sub$gt;2$lt;/sub$gt;的磁和磁热性能研究

在一些磁性材料内, 磁性离子间交换作用和磁性离子的自旋涨落对材料磁性有影响. 本文根据磁比热实验值确定了晶场参数后, 利用包含自旋涨落的交换作用有效场H_m= n₀ (1 + γ T + β e^{ω T})M, 计算了PrNi₂晶体晶场能级的Zeeman劈裂. 在温度为3.8 K ≤T≤ 30 K范围内, 计算了该晶体多晶磁矩随外磁场的变化, 以及外磁场H=5000 Oe时磁化率倒数随温度的变化, 计算结果和实验值符合较好. 当外磁场在0–50000 Oe时, 计算的该晶体的磁熵变与已有文献的理论结果相似. 计算结果说明, 提出的包含自旋涨落的交换作用有效场不仅适合亚铁磁性晶体, 而且也适合顺磁性晶体. 关键词： 2')" href="#">PrNi₂ 磁比热 交换作用有效场 磁矩 磁熵变     

KCdF3晶体中Cr3+-Li+中心局域结构研究

利用零场分裂参量与晶体结构之间的定量关系,研究了双掺杂晶体KCdF₃:Cr³⁺,Li⁺的局域结构。指出,对于KCdF₃:Cr³⁺,Li⁺晶体,四角晶场的形成包含两个方面:(1)由于电荷补偿而产生的等效电荷形成的四角对称晶场;(2)Cr³⁺的局域结构发生晶格畸变而产生的四角对称晶场。事实上,当Cr³⁺和Li⁺掺入KCdF₃晶体时,Cr³⁺代替了Cd²⁺离子;由于Cr³⁺离子与Cd²⁺离子的半径不同、电荷不同、质量不同,导致Cr³⁺的局域结构发生晶格畸变,由此而产生四角对称晶场;由于电荷补偿,Li⁺离子取代了[001]方向与Cr³⁺离子邻近的Cd²⁺离子,由此产生的等效电荷而形成的四角晶场。这样,Cr³⁺的局域结构由O_h对称变为C_4v点对称。文中建立了ZFS参量和晶体结构之间的定量关系。在考虑晶格畸变和等效电荷的基础上,研究了KCdF₃:Cr³⁺,Li⁺晶体的ZFS参量,理论结果和实验符合很好。得到了F^-离子向中心离子分别移动为ΔR₁=0.00268nm,ΔR₂=0.001nm,ΔR₃=0.00165nm。     

掺入Mg2+对CsNiCl3晶体的基态能级、零场分裂参量及Jahn-Teller效应的影响

应用不可约张量理论构造了三角对称晶场中3d²/3d^８态离子的45阶可完全对角化的微扰哈密顿矩阵，在考虑了以前工作中被忽略的自旋-自旋耦合作用的基础上计算了CsNiCl₃晶体和CsNiCl₃:Mg²⁺晶体的基态能级、晶体结构、零场分裂参量和Jahn-Teller效应，研究了掺入Mg²⁺对CsNiCl₃晶体的光谱、零场分裂参量及Jahn-Teller效应的影响和自旋单重态对基态能级的贡献，发现掺杂使得晶体结构产生畸变，从而改变晶体光谱的精细结构和零场分裂参量，不改变Jahn-Teller效应的分裂规律但改变分裂的大小. 关键词： 基态能级 掺杂 零场分裂 自旋-自旋耦合     

(φ4As) CuCl3晶体中Cu2+-Cu2+离子对的EPR研究

本文在晶场理论的基础上,考虑了Cu²⁺-Cu²⁺离子间的交换作用后,得到了(φ₄As) CuCl₃晶体中Cu^2--Cu^2-离子对的跃迁能级,g-因子和零场分裂,计算结果与实验符合较好。     

溶液旋涂法制备BixY3-xFe5O12薄膜的自旋输运特性

钇铁石榴石(yttrium iron garnet,YIG)的自旋输运特性一直是自旋电子学的研究重点之一.Bi作为YIG最常见的掺杂元素,其薄膜Bi_xY_3-xFe₅O₁₂的磁光特性已经被广泛研究.但Bi³⁺取代Y³⁺对YIG自旋输运的影响规律还没有被系统地研究过.本文利用溶液旋涂法制备了不同掺杂比的Bi_xY_3-xFe₅O₁₂薄膜,并研究Bi掺杂对YIG薄膜形貌结构和自旋输运性能的影响.结果表明Bi掺杂没有改变YIG的晶体结构,掺杂比上升令薄膜的吸收强度增大,带隙减小.XPS表明了Bi³⁺和Bi²⁺的存在.Bi掺杂在自旋输运上的调控体现在Bi_xY_3-xFe₅O₁₂薄膜的磁振子扩散长度相比纯YIG薄膜有所减小.同时研究发现Pt/Bi_x...     

ZnS:Co2+晶体顺磁g因子的理论研究

提出了一个计算二元半导体中过渡金属(TM)离子顺磁g因子的共价模型,并用以计算了ZnS:Co²⁺晶体的g因子,计算值与实验值吻合很好,从而解决了用经典方法得到的g因子值与实验值相比偏小的问题.同时,通过对ZnS:Co²⁺晶体晶场光谱和顺磁g因子的分析,本文建议,在ZnS:Co²⁺晶体中,Co²⁺离子的t_2g电子和e_g电子部分处于反键轨道部分处于成健轨道.     

Co掺杂对铁磁金属La0.8Sr0.2MnO3磁电阻影响机理

通过对La_0.8Sr_0.2Mn_1-yCo_yO₃(y≤02)饱和磁矩和输运的测量,研究了Co对La_0.8Sr_0.2MnO₃的磁电阻影响机制.结果表明,在La_0.8Sr_0.2Mn_1-yCo_yO₃（y≤02）中Co³⁺离子是低自旋态.由于Mn³⁺—O—Co³⁺—O—Mn³⁺类型的磁交换与Mn³⁺-Mn⁴⁺离子间双交换作用相比较弱,Curie温度T_C附近的磁电阻随着Co掺杂量的增加而降低.与此相反,由于Co²⁺离子与e_g巡游电子的反铁磁交换耦合作用,低温区间的磁电阻随着Co掺杂量的增加而升高. 关键词： 低自旋 磁电阻 磁交换作用     

Nd3+:GdScO3晶体场能级及拟合分析

采用提拉法生长出了钕掺杂钪酸钆晶体(Nd³⁺:GdScO₃),通过低温吸收光谱和室温发射光谱,对其中Nd³⁺的实验能级进行分析指认,确定了Nd³⁺:GdScO₃的66个实验Stark能级,拟合了其自由离子参数和晶体场参数,拟合均方根误差为13.17 cm^-1.与Nd³⁺:YAP和Nd³⁺:YAG相比, Nd³⁺:GdScO₃的晶场强度较弱.弱的晶体场强度有可能是Nd³⁺:GdScO₃晶体具有优良激光特性的原因之一.本文数据集可在https://www.doi.org/10.57760/sciencedb.15702中访问获取.     

Crystal growth,luminescence and scintillation properties of Eu2+:CeBr3 crystals

Eu²⁺:CeBr₃ crystals were grown by vertical Bridgman growth method and slight aliovalent doping of Eu²⁺ in the CeBr₃ crystal did not change the crystal structure. The X-ray stimulated luminescence, photoluminescence, decay kinetics and scintillation properties were investigated at room temperature. The X-ray stimulated luminescence spectra exhibited wide broad emission bands from 3.54 eV to 2.95 eV in the Eu²⁺:CeBr₃ crystal with high content of 620 ppm of Eu²⁺, which were the overlap of the emission bands ascribed to 5d → 4f transition of Ce³⁺ and 4f⁶5 d¹ → 4f⁷ transition of Eu²⁺, respectively. When the content of Eu²⁺ was decreased to 70 ppm, another emission band centered at 2.29 eV was observed. The photoluminescence spectra showed the energy transfer from Ce³⁺ to Eu²⁺. This decreased the Ce³⁺ emission intensity but enhanced the Eu²⁺ emission intensity. The photoluminescence decay time of Ce³⁺ emission decreased from 14 ns to 10 ns when the content of Eu²⁺ increased from 70 ppm to 620 ppm. The decay time of the emission of 525 nm did not change with the excitation wavelength and Eu²⁺ content, which could be assigned to the excitons that were bound on Eu²⁺ related centers. The light output of the Eu:CeBr₃ crystal under the excitation of ²⁴¹Am radioactive source was less than 20.2% of Tl:NaI crystal.     

Efficiently visible and 2 μm infrared emission in K2YbF5: Ce3+/Ho3+ microcrystals

Ho³⁺/Ce³⁺ co-doped K₂YbF₅ microcrystals were synthesized by solvent-thermal method. Under excitation of 980 nm laser diode, effectively visible and 2 μm-infrared luminescence of Ho³⁺ ion were obtained in the microcrystals. By changing Ce³⁺-ion doping concentration, the luminescence properties of visible and 2 μm emission were effectively regulated. At low Ce³⁺-ion doping level, the red and green upconversion emission obviously increases and decreases respectively with the increase of Ce³⁺-ion amount in the samples, meanwhile the intensity of 2 μm fluorescence changes very little. At high Ce³⁺-ion doping level, the intensities of the red and green emission both decrease with the increase of Ce³⁺-ion concentration, while the 2 μm emission intensity increases obviously. In the sample doped with 16% Ce³⁺ ion, the intensity of 2 μm emission is about 4.5 times that of the sample without Ce³⁺ ion, and the corresponding quantum efficiency is about 78.3%. The result is attributed to the influence of the different cross relaxation between Ho³⁺ and Ce³⁺ ion in luminescence process at low and high Ce³⁺-ion doping concentration. The corresponding luminescence mechanism and energy transfer process were discussed in detail.     

Ce3+ 掺杂高密度氧化物玻璃的闪烁性能研究

用高温熔融法制备了以SiO₂-B₂O₃-Al₂O₃-Gd₂O₃为基质系统Ce³⁺掺杂的玻璃样品, 测试样品的密度、紫外——可见透射光谱、紫外激发光谱和主要的闪烁性能, 并且把一部分闪烁性能和PbWO晶体及BGO晶体做比较. 着重研究了不同Ce³⁺掺杂浓度与Gd³⁺ 离子的含量对玻璃样品闪烁性能的影响规律. 结果表明: 玻璃样品具有较大的密度; 样品的X射线激发发射光谱发射峰位置都在390 nm左右, 当Ce³⁺ 离子的掺杂浓度为1.0 mol%(摩尔分数)、Gd₂O₃含量为15 mol%时, 玻璃样品的发光峰强度达到BGO晶体发光强度的90%; 同样验证了Ce³⁺ 离子具有浓度猝灭效应; Gd³⁺可以敏化Ce³⁺离子发光, 但是Gd³⁺离子到达一定浓度时, 反而会产生猝灭效应, 降低了Ce³⁺ 离子的发光. Ce³⁺ 离子掺杂SiO₂-B₂O₃-Al₂O₃-Gd₂O₃系统的闪烁玻璃有望替代闪烁晶体广泛应用于高能物理中.     

掺Ga对ZnO电子态密度和光学性质的影响

采用密度泛函理论下的第一性原理平面波赝势方法,研究了掺Ga对纤锌矿ZnO电子态密度和光学性质的影响.从晶体配位场理论分析了掺Ga前后ZnO的成键情况及态密度的变化.计算得到掺Ga后电子浓度为2.42×10²¹ cm^-3,ZnO的载流子浓度提高了10⁴倍.比较分析掺Ga前后ZnO的介电函数、复折射率、吸收光谱和反射光谱可得,ZnO光吸收边向高能端移动,光学带隙增大.在可见光区,ZnO光吸收系数与反射率减小,光透过率显著提高,使ZnO:Ga成为 关键词： 密度泛函理论 态密度 光学性质 ZnO:Ga     

Tunable exchange bias in La1.5Sr0.5CoMnO6 double perovskite doped with nonmagnetic Ga ions

The crystal structure, electronic structure, and magnetic behaviors of nonmagnetic Ga ions doped double perovskite La_1.5Sr_0.5CoMnO₆ single phase crystals have been investigated. Different from the traditional magnetic dilution effect of nonmagnetic doping, Ga doping in La_1.5Sr_0.5CoMnO₆ enhances the ferromagnetic (FM) exchange interaction of Co³⁺-O-Mn³⁺. Moreover, both conventional and spontaneous exchange bias (EB) effects can be tuned by modulating the Ga doping content, which is accompanied by the variation of the Co^3+/4+ and Mn^3+/4+ and the effective magnetic moment. The EB field and magnetization can be improved by nonmagnetic Ga³⁺ doping with content lower than 0.2. The evolution of conventional and spontaneous EB effects in La_1.5Sr_0.5Co_1-xGa_xMnO₆ can be understood in terms of the unidirectional interface anisotropic coupling between FM/anti-FM, and/or FM/spin glass, which is affected by antisite disorder, spin glass, and the uncompensated coupling between Co and Mn.     

5d-level energies of Ce and the crystalline environment. IV. Aluminates and “simple” oxides

Information on the energy of 5d-levels of Ce³⁺ ions in aluminates and “simple” oxides has been collected. The crystal field splitting of the 5d-levels is interpreted in terms of the type and size of anion polyhedron coordinating the Ce³⁺ ion. The centroid (barycenter) shift of the 5d-configuration is analyzed by a ligand polarization model providing values for the spectroscopic polarizability α_sp of the anion ligands. The data provide evidence that the centroid shift behaves independently from the crystal field splitting. By combining centroid shift and crystal field splitting, the “spectroscopic” redshift of the first electric dipole-allowed fd transition of Ce³⁺-doped in the compounds will be interpreted. The large crystal field splitting in garnet compounds and the small splitting in perovskite compounds will be discussed.     

Effects of La3+ doping on the optical characteristics and color tunability of (Mg,Mn)(Y,Ce, La)4Si3O13 phosphors

The doping effects of La³⁺ ions on the photoluminescence properties and color tunability of (Mg, Mn)(Y, Ce, La)₄Si₃O₁₃ phosphors have been elaborated in this study. On increasing the La³⁺ concentration in the host, tunability of excitation wavelength is achieved first, which in turn leads to the blue shift in the wavelength of Ce³⁺ emission. The high-energy emission shift of Ce³⁺ ions results from the change in the crystal field around Ce³⁺ ions. With the incorporation of La³⁺ ions, the chromaticity coordinates shift towards white-light region showing the tunable characteristics. Moreover, the correlated color temperature (CCT) change from warm white to cool white light region with different concentration of La³⁺ ions. The variation of different excitation wavelength tunes the emission thus augmenting the probability of (Mg, Mn)(Y, Ce, La)₄Si₃O₁₃ phosphors for potential application in optical devices.     

敏化离子Ce3+对Er3+∶YAG的1.6μm波长激光性能的影响

测定了Ce³⁺,Er³⁺∶YAG中Ce³⁺离子的吸收截面.用从能级跃迁速率方程和激光传输方程推出的表达式计算了1.6μm波长激光的阈值能量(功率)和斜率效率.表明在Ce³⁺,Er³⁺∶YAG中,Ce³⁺对Er³⁺离子的激光性能影响与激活离子Er³⁺的浓度、晶棒大小有关.短晶棒或浓度低的晶体加入Ce³⁺可降低Er 关键词：     

Effect of Melting Times on the Down-Shifting Properties in Ce<Superscript>3+</Superscript>-Doped Oxyfluoride Glass Ceramics for a-Si Solar Cells

We synthesize Ce³⁺-doped oxyfluoride glass ceramics (GCs) with different melting times employing the conventional melt-quenching method. We investigate the crystal structure and photoluminescence properties of Ce³⁺-doped GCs in detail in order to evaluate the effect of melting times on the downshifting properties. The photoluminescence properties revealed that the Ce³⁺ doped GCs have an intense emission band in the broad region from 480 to 600 nm under 427 nm excitation. We improve the energy-conversion efficiency of a-Si solar cells by 0.41%, from 5.02% to 5.43%, by incorporating the Ce³⁺-doped GCs with a melting time of 1.5 h. The above results indicate that Ce³⁺-doped GCs can be a promising candidate as downshifting materials for applications in a-Si solar cells.     

Family of paramagnetic centers of Ce3+ ions in yttrium aluminum garnet

The electron paramagnetic resonance (EPR) spectra of Ce³⁺ ions in single crystals of yttrium aluminum garnet have been investigated. It has been found that, in addition to the usually observed EPR signals of Ce³⁺ ions located in the regular environment at dodecahedral sites of the crystal lattice, the spectra contain a group of less intense anisotropic lines with g-factors close to the corresponding parameters of Ce³⁺ ions in the regular environment. It has been concluded that the observed satellite lines belong to the family of Ce³⁺ ions in the immediate vicinity of which there are permutation defects that lead to a change in the strength and symmetry of the crystal field in the vicinity of the paramagnetic center.