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1.
使用对Zn2N3:Mn薄膜热氧化的方法成功制备了高含N量的Mn和N共掺ZnO的稀磁半导体薄膜.在没有N离子共掺的情况下,ZnO:Mn薄膜的铁磁性非常微弱;如果进行N离子的共掺杂,就会发现ZnO:Mn薄膜在室温下表现出非常明显的铁磁性,饱和离子磁矩为0.23 μB—0.61 μB.这说明N的共掺激发了ZnO:Mn薄膜中的室温铁磁性,也就是受主的共掺引起的空穴有利于ZnO中二价Mn离子的铁磁性耦合,这和最近的相关理论研究符合很好.
关键词:
磁性半导体
受主掺杂
空穴媒介的铁磁性 相似文献
2.
This paper reports the paramagnetic behavior of Mn doped ZnO co-doped with rare earth (Gd and Sm) atoms. The formation of secondary rare earth oxides (Gd2O3 and Sm2O3) is confirmed from the X-ray diffraction patterns. The rare earth oxides in the system forbids the grain growth and interconnection between the grains. The weak link between the grains suppresses the long range exchange interaction between the Mn ions and hence, reduces the ferromagnetic ordering. Owing to the large mismatch between ionic radii of rare earth and transition metal atoms inside the matrix, the rare earth element cannot contribute to promote ferromagnetic behavior in Mn doped ZnO, irrespective of their high individual magnetic moments. 相似文献
3.
Effect of RE3+ as a co-dopant in long-lasting phosphorescence CdSiO3:Mn2+ (RE=Y, La, Gd, Lu) has been investigated. A longer orange emitting phosphorescence phenomenon was observed in the co-doped CdSiO3:Mn2+,RE3+ phosphors after exciting with ultraviolet (UV) light. The luminescence properties, including photoluminescence (PL) spectra and thermoluminescence (TL) spectra, as well as the afterglow decay curves, were studied. The results revealed that one of the origins of the improvement is due to nonequivalent substitution to produce more e-traps, and energy transfer from Gd3+ to Mn2+ to boost the performance of CdSiO3:Mn2+,Gd3+. Role of RE3+ co-doped into CdSiO3:Mn2+ matrix and the possible long-lasting phosphorescence process are discussed in this paper. 相似文献
4.
Kongping Wu Shulin Gu Kun Tang Shunming Zhu Mengran Zhou Yourui Huang Mingxiang Xu Rong Zhang Youdou Zheng 《Physica B: Condensed Matter》2012,407(13):2429-2433
Mn doped Zinc oxide (ZnO) thin films were prepared by metal organic chemical vapor deposition (MOCVD) technique. Structural characterizations by X-ray diffraction technique (XRD) and photoluminescence (PL) indicate the crystal quality of ZnO films. PL and Raman show a large fraction of oxygen vacancies (VO2+) are generated by vacuum annealed the film. The enhancement of ferromagnetism in post-annealed (Mn, In) codoped ZnO could result from VO2+ incorporation. The effect of VO2+ on the magnetic properties of (Mn, In) codoped ZnO has been studied by first-principles calculations. It is found that only In donor cannot induce ferromagnetism (FM) in Mn-doped ZnO. Besides, the presence of VO2+ makes the Mn empty 3d-t2g minority state broadened, and a t2g-VO2+ hybrid level at the conduction band minimum forms. The presence of VO2+ can lead to strong ferromagnetic coupling with the nearest neighboring Mn cation by BMP model based on defects reveal that the ferromagnetic exchange is mediated by the donor impurity state, which mainly consists of Mn 3d electrons trapped in oxygen vacancies. 相似文献
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6.
E.K. Abdel-Khalek A.F. Salem A.A. Bahgat 《Journal of magnetism and magnetic materials》2010,322(8):909-914
The magnetic properties of RE0.7Ca0.3Mn0.95Fe0.05O3 perovskite with rare-earth cations (RE=Sm and Gd) were investigated by means of X-ray diffraction, Mössbauer spectroscopy, and low temperature (4.2-266 K) magnetization measurements. Structural characterization of these compounds shows that they both have orthorhombic (Pbnm) structure. The Mössbauer spectra show clear evidence of local structural distortion of the Mn(Fe)O6 octahedron, which is based on the non-zero nuclear quadrupole interactions for high-spin Fe3+ ions. It was found that the local structural distortion increases significantly when Sm3+ is replaced by Gd3+. This distortion is attributed to the Jahn-Teller coupling strength as estimated from the Mössbauer effect results. The magnetic results indicate that the Curie temperature decreases as a result of replacing Sm by Gd. This is due to the decrease of the average A-site cationic radius 〈rA〉. The rapid increase of magnetization at low temperature indicates the magnetic ordering of rare earth ions at the A-site. 相似文献
7.
The electronic and magnetic properties of (Mn,C)-codoped ZnO diluted magnetic semiconductor
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The electronic and magnetic properties of (Mn,C)-codoped ZnO are studied in the Perdew-Burke-Ernzerhof form of generalized gradient approximation of the density functional theory. By investigating five geometrical configurations, we find that Mn doped ZnO exhibits anti-ferromagnetic or spin-glass behaviour, and there are no carriers to mediate the long range ferromagnetic (FM) interaction without acceptor co-doping. We observe that the FM interaction for (Mn,C)-codoped ZnO is due to the hybridization between C 2p and Mn 3d states, which is strong enough to lead to hole-mediated ferromagnetism at room temperature. Meanwhile, we demonstrate that ZnO co-doped with Mn and C has a stable FM ground state and show that the (Mn,C)-codoped ZnO is FM semiconductor with super-high Curie temperature (T C = 5475 K). These results are conducive to the design of dilute magnetic semiconductors with codopants for spintronics applications. 相似文献
8.
The magnetic properties of ZnO co-doped with 5 at. % Co and 5 at. % Mn(Zn0.90Co0.05Mn0.05O) synthesized by a solid-state reaction were investigated by means of 57Co emission Mössbauer spectroscopy. The majority of the probe ions (80 %) residing in defect-free substitutional Zn sites take the oxidation state of 57Fe 2+, and the others presumably form local defects taking the state of 57Fe 3+ at room temperature. Both components show doublets, and RT ferromagnetism was thus absent in the sample. For the measurement at 10 K, spectral broadening was observed, implying a possible presence of a weak magnetic component. 相似文献
9.
《Journal of magnetism and magnetic materials》2002,238(2-3):293-300
A systematic study of the magnetic and transport properties of the system (La1−xGdx)0.67Ca0.33MnO3 (0⩽x⩽1) is presented in this article. Through this series, a great crystallographic distortion is achieved but keeping constant the electronic density. At low Gd3+ content, these ions behaves in a paramagnetic state following a Brillouin function. Low-temperature ferromagnetism remains unchanged. However, for the samples with large Gd3+ content a complex magnetic behavior arises from several competing interaction as super-exchange, double-exchange and also the interaction between Gd and Mn ions. Resistivity and thermopower follow a progressive increase as Gd3+ content does, but the polaron energy in the paramagnetic range remains independent of all these changes. Thermopower infinite value is also determined and analyzed. 相似文献
10.
Langsheng Ling Lei Zhang Zhitao Zhang Li Pi Shun Tan Yuheng Zhang 《Solid State Communications》2009,149(29-30):1168-1172
The magnetic properties of Y 0.35Ln0.05Ca0.6MnO3 (Ln = La, Pr, Nd, Sm, Gd, Dy) have been investigated thoroughly. The small average cationic radius of the present system results in a short-range antiferromagnetic charge-ordering (AFM-CO) state in the manganites. With the decrease of temperature, a super-exchange interaction begins to establish itself between the remaining disordered Mn ions after the formation of the short-range CO state. Then, the reentrant cluster-glass state originates from the frustration between the FM order in the clusters and the AFM interactions present in the background matrix. However, the large magnetic moments of Gd3+ and Dy3+ ions apply an internal magnetic field on the Mn3+ and Mn4+ ions, which results in the suppression of the cluster-glass state. 相似文献
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12.
X.J. Liu Z.Q. Li A. Yu M.L. Liu W.R. Li B.L. Li P. Wu H.L. Bai E.Y. Jiang 《Journal of magnetism and magnetic materials》2007
We have investigated the magnetic, electrical transport and electron spin resonance (ESR) properties of polycrystalline Fe-doped manganite LaMn0.7Fe0.3O3+δ prepared by sol–gel method. A typical cluster-glass feature is presented by DC magnetization and AC susceptibility measurements and a sharp but shallow memory effect was observed. Symmetrical Lorentzian lines of the Mn/Fe spectra were detected above 120 K, where the sample is a paramagnetic (PM) insulator. When the temperature decreases from 120 K, magnetic clusters contributed from ferromagnetic (FM) interaction between Mn3+ and Mn3+/Fe3+ ions develop and coexist with PM phase. At lower temperature, these FM clusters compete with antiferromagnetic (AFM) ones between Fe3+ ions, which are associated with a distinct field-cooled (FC) effect in characteristic of cluster-glass state. 相似文献
13.
Electron magnetic resonance (EMR) spectra of gadolinium-doped zircon (ZrSiO4) powders have been studied at room temperature for gadolinium concentrations between 0.20 and 1.0 mol%. The results suggest that Gd3+ ions occupy substitutional sites in the zircon lattice, that the electron magnetic resonance linewidth increases with increasing gadolinium concentration and that the range of the exchange interaction between Gd3+ ions is about 1.17 nm, larger than that of the same ion in other host lattices, such as ceria (CeO2), strontium oxide (SrO) and calcium oxide (CaO). The fact that the electron magnetic resonance linewidth of the Gd3+ ion in polycrystalline zircon increases, regularly and predictably, with Gd concentration, shows that the Gd3+ ion can be used as a probe to study, rapidly and non-destructively, the crystallinity and degradation of ZrSiO4. 相似文献
14.
M. Forker J. C. Soares K. Krien F. Reuschenbach K. Freitag 《Zeitschrift für Physik B Condensed Matter》1978,29(4):313-317
The magnetic hyperfine field at dilute Hg impurities in Gd has been investigated by the conversion electron (e
–)--time differential perturbed angular correlation (TDPAC) technique. The radioactivities197m
Hg and199Tl were implanted into Gd foils by means of an isotope separator. TDPAC measurements were performed with the 165 keV-L-conversion electron—134 keV--cascade of197Hg at different temperatures and with the 334 keV--158 keV-K-conversion electron cascade of199Hg at 200 K.The regular site occupation probabilities were found to be 15(3)% for an annealed197m
HgGd sample and 29(5)% in unannealed199TlGd samples.From the magnetic hyperfine interaction frequencies measured for the regular sites at 200 K the magnetic hyperfine fields |H
hf(197HgGd; 200 K)|=256(13) kG and |H
hf(199HgGd; 200 K)|=267(7) kG were deduced.On leave from the University of Lisboa, Portugal 相似文献
15.
The purpose of the present study is to develop an understanding of photoluminescence properties of Dy3+, Mn2+ or Gd3+doped NaCaPO4 phosphors, which have served as efficient phosphors in many industrial applications. The phase formation was confirmed by the X-ray powder diffraction (XRD) measurement. Photoluminescence (PL) excitation spectrum measurement of NaCaPO4:Dy3+ shows this phosphor can be efficiently excited by near-ultraviolet (UV) light from 300 to 400 nm and presents dominant luminescence band centered at 480 nm (blue) and 573 nm (yellow). The PL excitation of NaCaPO4:Mn2+ and Gd3+ under UV wavelength shows the emissions at 520 and 313 nm, respectively. A scanning electron microscope (SEM) shows an average crystallite size in sub-micrometer range. The obtained results show that the phosphors have the potential for application in the lamp industry and medical applications. 相似文献
16.
The Ag metallic host doped with Gd and Sb is an excellent model system to study the bottleneck effect associated to the conduction-electron (c-e) spin-flip scattering mechanism. Electron spin resonance of Gd3+ in both, Ag-(Gd doped)- and Ag-(Gd and Sb doped)-systems, reveal the presence of bottleneck which can be tuned by the amount of Gd and Sb impurities. The increase of the Gd concentration leads to a c-e spin-flip relaxation rate to the magnetic Gd3+ ions larger than that to the lattice, favoring the bottleneck regime. Whereas the effect of the non-magnetic impurities (Sb ions) is to increase, via spin–orbit scattering, the spin-flip relaxation rate of the c-e to the lattice, weakening the bottleneck regime. 相似文献
17.
运用基于密度泛函理论的第一性原理,对Hg2CuTi型Mn2NiGe的四方变形、晶体结构、磁性、电子结构、压力响应等进行了计算.计算结果表明: 1)在由立方结构至四方结构的转变中,在c/a约为1.34处存在一个稳定的马氏体相;2)在奥氏体态和马氏体态下,Mn原子均是Mn2NiGe总磁矩的主要贡献者,但Mn(A),Mn(B)原子磁矩的值不等且呈反平行耦合,因而Mn2N
关键词:
第一性原理
磁性形状记忆
四方变形
马氏体相变 相似文献
18.
采用射频磁控溅射法在石英玻璃衬底上制备了ZnO:Mn薄膜, 结合N+ 注入获得Mn-N共掺ZnO薄膜, 进而研究了退火温度对其结构及室温铁磁性的影响. 结果表明, 退火后ZnO:(Mn, N) 薄膜中Mn2+和N3-均处于ZnO晶格位, 没有杂质相生成. 退火温度的升高 有助于修复N+注入引起的晶格损伤, 同时也会让N逸出薄膜, 导致受主(NO)浓度降低. 室温铁磁性存在于ZnO:(Mn, N)薄膜中, 其强弱受NO浓度的影响, 铁磁性起源可采用束缚磁极化子模型进行解释. 相似文献
19.
D. Zayachuk Ye. Polyhach E. Slynko O. Khandozhko C. Rudowicz 《Applied magnetic resonance》2003,24(3-4):369-377
An electron paramagnetic resonance (EPR) experimental study of crystalline and powder p-Pb1?x?y Sn y Gd y Te samples for various matrix compositionx and Gd contenty has been carried out. The study reveals that grinding the crystals into powder as well as their low-temperature annealing turns Gd impurity ions from the EPR-silent Gd2+ state to the EPR-active Gd3+ state, whereas high-temperature annealing in vacuum quenches EPR signals from Gd3+ ions. The experimental results are interpreted in terms of a model assuming that the trivalent charge state of the Gd impurity ions in lead and tin tellurides is a component part of the “substituting Gd impurity-Te vacancy” complex. 相似文献
20.
The electron paramagnetic resonance of Mn2+ and Gd3+ doped in Pr2Zn3(NO3)12.24H2O single crystals has been studied at X-band. Mn2+ substitutes for two Zn2+ sites, while Gd3+ substitutes for single type of Pr3+ sites. The spin-Hamiltonian analysis of the EPR spectra is presented at 298 K as well as 77 K. 相似文献