18 results on '"Mei, Liang-mo"'
Search Results
2. Long-ranged and high temperature ferromagnetism in (Mn,C)-codoped ZnO studied by first-principles calculations.
- Author
-
Lin, Xue-ling, Yan, Shi-shen, Zhao, Ming-wen, Hu, Shu-jun, Yao, Xin-xin, Han, Chong, Chen, Yan-xue, Liu, Guo-lei, Dai, You-yong, and Mei, Liang-mo
- Subjects
PHYSICS research ,FERROMAGNETISM ,SEMICONDUCTOR industry ,SEMICONDUCTOR doping ,MAGNETIC semiconductors - Abstract
We theoretically investigated the electronic structures and magnetic properties of (Mn,C)-codoped ZnO system based on the first-principles calculations within a GGA+U
p,d approach. We found that codoping C is a promising approach to enhance the ferromagnetic coupling between the nearest-neighboring Mn ions due to the strong hybridization between the C:2p and the Mn:3d states. Moreover, the spin-polarized states induced by C are so extended that they can mediate long-ranged ferromagnetic exchange interactions beyond the nearest-neighboring case. Therefore, (Mn,C)-codoped ZnO is expected to be a ferromagnetic semiconductor with long-ranged ferromagnetism and high Curie temperature. [ABSTRACT FROM AUTHOR]- Published
- 2010
- Full Text
- View/download PDF
3. Magnetism of amorphous Ge1-xMnx magnetic semiconductor films.
- Author
-
Deng, Jiang-xia, Tian, Yu-feng, Yan, Shi-shen, Cao, Qiang, Liu, Guo-lei, Chen, Yan-xue, Mei, Liang-mo, Ji, Gang, and Zhang, Ze
- Subjects
MAGNETIC semiconductors ,HYSTERESIS loop ,HALL effect ,VACUUM technology ,FERROMAGNETISM ,THIN films - Abstract
Amorphous Ge
1-x Mnx magnetic semiconductor films with high Mn concentrations were prepared on liquid-nitrogen (LN2 )-cooled glass substrates by ultrahigh vacuum thermal coevaporation. Hysteresis loops measured at 5 K show coexistence of ferromagnetism and paramagnetism. The maximum Curie temperature of 220 K was found in Ge0.48 Mn0.52 film. Moreover, exchange bias occurs in magnetization hysteresis loops for samples with higher Mn concentrations, which can be explained by the antiferromagntic exchange coupling between ferromagnetic phase and antiferromagnetic phase. All the Ge1-x Mnx magnetic semiconductor films show semiconducting transport behavior and anomalous Hall effects below the Curie temperature, indicating carrier-mediated ferromagnetism. [ABSTRACT FROM AUTHOR]- Published
- 2008
- Full Text
- View/download PDF
4. Variations from Zn 1− x Co x O Magnetic Semiconductor to Co–ZnCoO Granular Composite
- Author
-
Yan Shi-Shen, Liu Guo-Lei, Ren Miao-Juan, Mei Liang-Mo, and Chen Yan-Xue
- Subjects
Materials science ,Condensed matter physics ,Magnetoresistance ,Annealing (metallurgy) ,Composite number ,General Physics and Astronomy ,Magnetic semiconductor ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Metal ,Condensed Matter::Materials Science ,Magnetization ,Ferromagnetism ,visual_art ,Thermal ,visual_art.visual_art_medium ,Condensed Matter::Strongly Correlated Electrons - Abstract
We investigate the variations from as-deposited Zn1−xCoxO magnetic semiconductors to the post-annealed Co–ZnCoO granular composite. The as-deposited Zn1−xCoxO magnetic semiconductor deposited under thermal non-equilibrium conditions is composed of Zn1−xCoxO nanograins of high Co concentration. The room-temperature ferromagnetism with high magnetization and large negative magnetoresistance are found in the as-deposited samples. By annealing, the samples become of granular composite consisting of the Co metal grains and the remanent Zn1−xCoxO matrix. Although the magnetization is enhanced after annealing, the spin-dependent negative magnetoresistance disappears at room temperature. The magnetoresistance observed in the annealed samples in the high field region has no relation with the ferromagnetism, which in turn indicates that the room-temperature ferromagnetism and large negative magnetoresistance observed in the as-deposited are the intrinsic properties of the Zn1−xCoxO magnetic semiconductor.
- Published
- 2007
5. Structures, Pd spacer polarization and magnetic properties of Co-Nb/Pd multilayers
- Author
-
Liu Yi-Hua, Yan Shi-Shen, T. P Ma, Li Min, R. C Barker, and Mei Liang-Mo
- Subjects
Diffraction ,Materials science ,Condensed matter physics ,Magnetometer ,Exchange interaction ,Physics::Optics ,General Physics and Astronomy ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Polarization (waves) ,Ferromagnetic resonance ,Electron transport chain ,law.invention ,Condensed Matter::Materials Science ,Magnetization ,Ferromagnetism ,law - Abstract
Magnetic multilayers [Co-Nb(1.5 or 3.6 nm)/Pd(x nm)]40 were fabricated by radio frequency sputtering synthesis. The structures and magnetic properties of the Co-Nb/Pd multilayers were studied by x-ray diffraction, vibrating sample magnetometer, torque magnetometer and ferromagnetic resonance measurements. The oscillatory dependence of the phase structure, the strain, the ferromagnetic interlayer coupling and the spacer polarization of multilayers on the increase of Pd spacer thickness was observed. The relationship among phase structure, strain, interlayer coupling and the polarization of Pd spacers was discussed. The magnetic polarization of Pd spacers will enhance the ferromagnetic coupling between magnetic layers and will restrain antiferromagnetic coupling to occur. The spin-dependent electron transport along the normal direction of multilayers and its exchange interaction play key roles in causing these oscillatory behaviors.
- Published
- 1997
6. Magnetic polarization of spacer Pd layer and magnetic properties of Co/Pd multilayers
- Author
-
Zhao Jian-Gao, Zheng Min, Ma Xiao-ding, Gu You-song, T. P Ma, Li Min, R. C Barker, Mei Liang-Mo, Liu Yi-Hua, and Mai Zhen-Hong
- Subjects
Materials science ,Magnetoresistance ,Condensed matter physics ,Magnetometer ,Physics::Optics ,General Physics and Astronomy ,Giant magnetoresistance ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Polarization (waves) ,law.invention ,Condensed Matter::Materials Science ,Magnetic anisotropy ,Magnetization ,Ferromagnetism ,law ,Antiferromagnetism ,Condensed Matter::Strongly Correlated Electrons - Abstract
Magnetic multilayers [Co(1.5 nm)/Pd(x nm)]40 grown by rf sputtering were studied by x-ray diffraction, vibrating sample magnetometer, torque magnetometer and magnetoresistance measurements. The dependences of the interfacial roughness and the structure perfectness of Co/Pd multilayers on the spacer Pd layer thickness have been revealed from x-ray diffraction data. An oscillatory variation of saturation magnetization versus the thickness of the Pd spacer was observed. A similar oscillatory behavior in the dependence of its magnetic anisotropy on the thickness of the Pd spacer was observed. It is suggested from these two phenomena that the magnetic polarization of Pd spacers oscillates between ferromagnetic and antiferromagnetic polarization with the increase of Pd spacer thickness under a RKKY-like interaction. Evidence is found for the antiferromagnetic polarization of the inner-part of the Pd spacer. The antiferromagnetic coupling between two Co layers and giant magnetoresistance effect in Co/Pd multilayer system were not observed. The relationship among structure, interlayer coupling and magnetic polarization effect of the Pd spacer was discussed.
- Published
- 1997
7. Magnetic polarization of Pd spacers and oscillatory exchange coupling between Fe and Pd layers in Fe/Pd multilayers
- Author
-
Liu Yi-Hua, Li Min, Mei Liang-Mo, Xie Shi-Jie, and Xu Rong-li
- Subjects
Coupling ,Materials science ,Condensed matter physics ,Magnetic moment ,General Physics and Astronomy ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Polarization (waves) ,Metal ,Condensed Matter::Materials Science ,Magnetization ,Ferromagnetism ,Conversion electron mössbauer spectroscopy ,visual_art ,visual_art.visual_art_medium ,Condensed Matter::Strongly Correlated Electrons - Abstract
An oscillatory behavior in specific saturation magnetization of Fe/Pd multilayers is observed. The conversion electron Mossbauer spectroscopy and other experiments indicate that this behavior is caused by the magnetic polarization of Pd spacers, which alternates between positive and negative polarization with respect to the magnetic moments of Fe layers. The interlayer coupling between two Fe layers always keeps ferromagnetic. Then, the interlayer couplings in ferromagnetic metal/nearly ferromagnetic metal multilayers were calculated by using the model of Barnas. The results of calculation prove that the above phenomenon might appear under some condition. The influence of magnetic polarization potential of spacers and interface chemical potential on the interlayer couplings is also discussed.
- Published
- 1996
8. Magnetic and Transport Properties of ZnO/Co Nanomultilayers
- Author
-
Ren Miao-Juan, Ji Gang, Yan Shi-Shen, Song Hong-Qiang, Mei Liang-Mo, and Chen Yan-Xue
- Subjects
Materials science ,Condensed matter physics ,Ferromagnetism ,Transmittance ,General Physics and Astronomy ,Sputter deposition ,Thermal conduction ,Quantum tunnelling - Abstract
[ZnO(0.5 nm)/Co(0.6 nm)]60 multilayers were fabricated by magnetron sputtering. The magnetic, transport and optical properties were studied. The ferromagnetic state at low temperature was demonstrated. Most of the grains in the samples will be unblocked when temperature is below 50 K. The measured magneto-resistance at 4.8 K is higher than 30%. This value is larger than any other reported data. The transport mechanism may come down to a combination of tunnelling conduction with the second-order hopping. Some small peaks on transmittance curves were found, the matter is still open.
- Published
- 2003
9. Oxide magnetic semiconductors: Materials, properties, and devices
- Author
-
Yan Shi-Shen, Tian Yu-Feng, Mei Liang-Mo, and Hu Shu-Jun
- Subjects
Materials science ,Dopant ,Magnetism ,Zinc compounds ,Oxide ,General Physics and Astronomy ,Nanotechnology ,Magnetic semiconductor ,Condensed Matter::Materials Science ,chemistry.chemical_compound ,Ferromagnetism ,chemistry ,Transition metal ,Electrical resistivity and conductivity - Abstract
We give a brief introduction to the oxide (ZnO, TiO2, In2O3, SnO2, etc.)-based magnetic semiconductors from fundamental material aspects through fascinating magnetic, transport, and optical properties, particularly at room temperature, to promising device applications. The origin of the observed ferromagnetism is also discussed, with a special focus on first-principles investigations of the exchange interactions between transition metal dopants in oxide-based magnetic semiconductors.
- Published
- 2013
10. Room-Temperature Anisotropic Ferromagnetism in Fe-Doped In 2 O 3 Heteroepitaxial Films
- Author
-
Jiao Jun, Tang Min-jian, Mei Liang-Mo, Yan Shi-Shen, Chen Yan-Xue, Xing Peng-fei, and Liu Guo-Lei
- Subjects
Diffraction ,Condensed Matter::Materials Science ,Magnetization ,Materials science ,Electron diffraction ,Ferromagnetism ,Condensed matter physics ,Condensed Matter::Superconductivity ,General Physics and Astronomy ,Coercivity ,Anisotropy ,Epitaxy ,Pulsed laser deposition - Abstract
Fe-doped In2O3 films are grown epitaxially on YSZ (100) substrates by pulsed laser deposition. The in-situ reflection high-energy electron diffraction, the atomic force microscopy, and the x-ray diffraction patterns show that the films have a well defined cubic structure epitaxially oriented in the (100) direction. Room temperature ferromagnetism is observed by an alternating gradient magnetometer. Strong perpendicular magnetic anisotropy with a remnant magnetization ratio of 0.83 and a coercivity of 2.5kOe is revealed. Both the structural and the magnetic measurements suggest that this ferromagnetism is an intrinsic property deriving from the spin-orbit coupling between the diluted Fe atoms.
- Published
- 2009
11. Magnetic Properties and Antiferromagnetic Coupling in Inhomogeneous Zn 1– x Fe x O Magnetic Semiconductor
- Author
-
J. P. Liu, Kai Sun, Sun Xiang-Cheng, Zhang Ze, V Chakka, B Altuncevahir, Mei Liang-Mo, Jie Lian, Yan Shi-Shen, Deng Jiang-Xia, and Wang Yong
- Subjects
Materials science ,Condensed matter physics ,Annealing (metallurgy) ,Oxide ,General Physics and Astronomy ,Magnetic semiconductor ,Magnetic susceptibility ,Antiferromagnetic coupling ,Condensed Matter::Materials Science ,chemistry.chemical_compound ,Paramagnetism ,chemistry ,Ferromagnetism ,Sputtering ,Condensed Matter::Strongly Correlated Electrons - Abstract
Zn1−xFexO inhomogeneous oxide magnetic semiconductor films with high Fe concentration are prepared by sputtering, and fast annealing is carried out at different temperatures. It is found that magnetic properties are greatly modulated by controlling the composition inhomogeneity and subsequently fast annealing. Both ferromagnetic and paramagnetic components are found to coexist in the as-deposited Zn1−xFexO magnetic semiconductor. In particular, the antiferromagnetic coupling between the neighbouring local ferromagnetic regions is found in the as-deposited Zn0.23Fe0.77 O film, and the antiferromagnetic coupling strength increases with increasing temperature from 110 K to 300 K. We believe that this unusual antiferromagnetic coupling is mediated by thermally activated hopping carriers.
- Published
- 2009
12. SPIN DENSITY WAVE OF ORGANIC FERROMAGNETS WITH OPEN ENDS
- Author
-
Xie Shi-Jie, Zhao Jun-Qing, Wang Shou-Guo, Wei Jian-Hua, and Mei Liang-Mo
- Subjects
Condensed Matter::Materials Science ,Chain structure ,Condensed matter physics ,Ferromagnetism ,Chain (algebraic topology) ,Chemistry ,General Physics and Astronomy ,Spin density wave ,Condensed Matter::Strongly Correlated Electrons ,Ring (chemistry) ,Spin-½ - Abstract
Spin density wave in organic ferromagnets with open ends was studied and the results were compared with that in a closed organic ferromagnet ring. It was found that an end-open chain structure is unfavorable for the formation of the ferromagnetic ground. The competition of electron-electron interactions and the π-electron-radical spin couplings and their different effect on the SDW in the main chain were discussed.
- Published
- 1999
13. Oscillation of coercivity between positive and negative in MnxGe1-x:H ferromagnetic semiconductor films.
- Author
-
Qin Yu-Feng, Yan Shi-Shen, Xiao Shu-Qin, Li Qiang, Dai Zheng-Kun, Shen Ting-Ting, Yang Ai-Chun, Pei Juan, Kang Shi-Shou, Dai You-Yong, Liu Guo-Lei, Chen Yan-Xue, and Mei Liang-Mo
- Subjects
FERROMAGNETISM ,SEMICONDUCTOR research ,MAGNETRONS ,COERCIVE fields (Electronics) ,HYDROGENATION - Abstract
Amorphous Mn
x Ge1-x : H ferromagnetic semiconductor films prepared in mixed Ar with 20% H2 by magnetron co-sputtering show global ferromagnetism with positive coercivity at low temperatures. With increasing temperature, the coercivity of Mnx Ge1-x :H films first changes from positive to negative, and then back to positive again, which was not found in the corresponding Mnx Ge1-x and other ferromagnetic semiconductors before. For Mn0.4 Ge0.6 :H film, the inverted Hall loop is also observed at 30 K, which is consistent with the negative coercivity. The negative coercivity is explained by the antiferromagnetic exchange coupling between the H-rich ferromagnetic regions separated by the H-poor non-ferromagnetic spacers. Hydrogenation is a useful method to tune the magnetic properties of Mnx Ge1-x films for the application in spintronics. [ABSTRACT FROM AUTHOR]- Published
- 2013
- Full Text
- View/download PDF
14. Ferromagnetism, variable range hopping, and the anomalous Hall effect in epitaxial Co:ZnO thin film.
- Author
-
Bai Hong-Liang, He Shu-Min, Xu Tong-Shuai, Liu Guo-Lei, Yan Shi-Shen, Zhu Da-Peng, Dai Zheng-Kun, Yang Feng-Fan, Dai You-Yong, Chen Yan-Xue, and Mei Liang-Mo
- Subjects
FERROMAGNETISM ,HALL effect ,COBALT ,MOLECULAR beam epitaxy ,ZINC oxide thin films ,SINGLE crystals ,CRYSTAL growth ,TEMPERATURE effect - Abstract
A series of high quality single crystalline epitaxial Zn
0.95 Co0.05 O thin films is prepared by molecular beam epitaxy. Superparamagnetism and ferromagnetism are observed when the donor density is manipulated in a range of 1018 cm-3 - 1020 cm-3 by changing the oxygen partial pressure during film growth. The conduction shows variable range hopping at low temperature and thermal activation conduction at high temperature. The ferromagnetism can be maintained up to room temperature. However, the anomalous Hall effect is observed only at low temperature and disappears above 160 K. This phenomenon can be attributed to the local ferromagnetism and the decreased optimal hopping distance at high temperatures. [ABSTRACT FROM AUTHOR]- Published
- 2012
- Full Text
- View/download PDF
15. Growth and photoluminescence properties of inclined ZnO and ZnCoO thin films on SrTiO3(110) substrates.
- Author
-
Bai Hong-Liang, Liu Guo-Lei, He Shu-Min, Yan Shi-Shen, Guo Hong-Yu, Ji Zi-Wu, Yang Feng-Fan, Chen Yan-Xue, and Mei Liang-Mo
- Subjects
PHOTOLUMINESCENCE ,ZINC oxide ,THIN films ,SUBSTRATES (Materials science) ,MOLECULAR beam epitaxy ,FERROMAGNETISM - Abstract
ZnO thin film growth prefers different orientations on the etched and unetched SrTiO
3 (STO)(110) substrates. Inclined ZnO and cobalt-doped ZnO (ZnCoO) thin films are grown on unetched STO(110) substrates using oxygen plasma assisted molecular beam epitaxy, with the c-axis 42° inclined from the normal STO(110) surface. The growth geometries are ZnCoO[100]//STO[11¯0] and ZnCoO[11¯1]//STO[001]. The low temperature photoluminescence spectra of the inclined ZnO and ZnCoO films are dominated by D0 X emissions associated with A0 X emissions, and the characteristic emissions for the2 E(2 G)→4 A2 (4 F) transition of Co2+ dopants and the relevant phonon-participated emissions are observed in the ZnCoO film, indicating the incorporation of Co2+ ions at the lattice positions of the Zn2+ ions. The c-axis inclined ZnCoO film shows ferromagnetic properties at room temperature. [ABSTRACT FROM AUTHOR]- Published
- 2012
- Full Text
- View/download PDF
16. Effect of native defects and Co doping on ferromagnetism in HfO.
- Author
-
Han, Chong, Yan, Shi-Shen, Lin, Xue-Ling, Hu, Shu-Jun, Zhao, Ming-Wen, Yao, Xin-Xin, Chen, Yan-Xue, Liu, Guo-Lei, and Mei, Liang-Mo
- Subjects
COBALT ,FERROMAGNETISM ,ELECTRONS ,MAGNETIC properties of metals ,HAFNIUM ,HYDROFLUORIC acid - Abstract
First-principles calculations of undoped HfO and cobalt-doped HfO have been carried out to study the magnetic properties of the dielectric material. In contrast to previous reports, it was found that the native defects in HfO could not induce strong ferromagnetism. However, the cobalt substituting hafnium is the most stable defect under oxidation condition, and the ferromagnetic (FM) coupling between the cobalt substitutions is favorable in various configurations. We found that the FM coupling is mediated by the threefold-coordinated oxygen atoms in monoclinic HfO and could be further enhanced in electron-rich condition. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2011 [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
17. Stoichiometry determined exchange interactions in amorphous ternary transition metal oxides: Theory and experiment
- Author
-
Mei, Liang-mo [School of Physics, National Key Laboratory of Crystal Materials, Shandong University, Jinan, Shandong 250100 (China)]
- Published
- 2014
- Full Text
- View/download PDF
18. Possible origin of ferromagnetism in un-doped ZnO: First-principles calculations
- Author
-
Lin, Xue-ling, Yan, Shi-shen, Zhao, Ming-wen, Hu, Shu-jun, Han, Chong, Chen, Yan-xue, Liu, Guo-lei, Dai, You-yong, and Mei, Liang-mo
- Subjects
- *
FERROMAGNETISM , *ZINC oxide , *ELECTRONIC structure , *MAGNETIC properties of metals , *WURTZITE , *TOPOLOGICAL defects (Physics) - Abstract
Abstract: We performed first-principles calculations to investigate the electronic structures and magnetic properties of neutral and charged intrinsic defects of wurtzite ZnO. Our results show that an isolated single charged Zn vacancy can introduce a magnetic moment of , and may be responsible for the unexpected ferromagnetism in the system. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.