1
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Duan L, Su J, Gong N, Wan B, Chen P, Zhou P, Wang Z, Li Z, Wu L. Pressure induced semiconductor-semimetal-superconductor transition of magnesium hexaborides. Dalton Trans 2019; 48:14299-14305. [PMID: 31453996 DOI: 10.1039/c9dt02813g] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A thorough structural exploration was performed for MgB6 combining the global structure searching method with first-principles calculations. Besides the known Cmcm phase, new phases, i.e. I4/mmm, C2/m-I, C2/m-II and P21/m, were predicted to be stable in the pressure range of 18-100 GPa. Unexpectedly, Cmcm-MgB6 was found to be a semiconductor with an indirect band gap of 0.38 eV with the HSE06 functional, in good agreement with the experimental finding. I4/mmm-MgB6 stabilized above 18 GPa exhibits semimetallic behaviour with a topological node-line near the Fermi level. Consequently, C2/m-I MgB6 with a sandwich structure similar to MgB2 is predicted to be a superconductor with a critical temperature (Tc) of 9.5 K. By analysing the electronic structure, the intriguing semiconductor-semimetal-superconductor transition may be ascribed to the delocalization of more B-p electrons in the boron sublattice. The novel functions uncovered for MgB6 may inspire more efforts to discover materials with intriguing properties.
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Affiliation(s)
- Li Duan
- State Key Laboratory of Metastable Materials Science and Technology, College of Material Science and Engineering, Yanshan University, Qinhuangdao 066004, Hebei, China.
| | - Jing Su
- State Key Laboratory of Metastable Materials Science and Technology, College of Material Science and Engineering, Yanshan University, Qinhuangdao 066004, Hebei, China.
| | - Ning Gong
- State Key Laboratory of Metastable Materials Science and Technology, College of Material Science and Engineering, Yanshan University, Qinhuangdao 066004, Hebei, China.
| | - Biao Wan
- State Key Laboratory of Metastable Materials Science and Technology, College of Material Science and Engineering, Yanshan University, Qinhuangdao 066004, Hebei, China.
| | - Peng Chen
- State Key Laboratory of Metastable Materials Science and Technology, College of Material Science and Engineering, Yanshan University, Qinhuangdao 066004, Hebei, China.
| | - Pengyuan Zhou
- State Key Laboratory of Metastable Materials Science and Technology, College of Material Science and Engineering, Yanshan University, Qinhuangdao 066004, Hebei, China.
| | - Zhibin Wang
- Key Laboratory of Applied Chemistry, College of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao 066004, Hebei, China
| | - Zhiping Li
- Key Laboratory of Applied Chemistry, College of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao 066004, Hebei, China
| | - Lailei Wu
- State Key Laboratory of Metastable Materials Science and Technology, College of Material Science and Engineering, Yanshan University, Qinhuangdao 066004, Hebei, China. and Key Laboratory of Applied Chemistry, College of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao 066004, Hebei, China
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2
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Gan LY, Wang R, Jin YJ, Ling DB, Zhao JZ, Xu WP, Liu JF, Xu H. Emergence of topological nodal loops in alkaline-earth hexaborides XB6(X = Ca, Sr, and Ba) under pressure. Phys Chem Chem Phys 2017; 19:8210-8215. [DOI: 10.1039/c6cp08421d] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Based on first-principles calculations, we report that external pressure can induce a topological phase transition in alkaline-earth hexaborides, XB6(X = Ca, Sr, and Ba).
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Affiliation(s)
- L.-Y. Gan
- Department of Physics
- South University of Science and Technology of China
- Shenzhen 518055
- China
- Key Laboratory of Advanced Technology of Materials (Ministry of Education)
| | - R. Wang
- Department of Physics
- South University of Science and Technology of China
- Shenzhen 518055
- China
- Institute for Structure and Function & Department of Physics
| | - Y. J. Jin
- Department of Physics
- South University of Science and Technology of China
- Shenzhen 518055
- China
| | - D. B. Ling
- Department of Physics
- Anhui University
- Hefei 230601
- China
| | - J. Z. Zhao
- Department of Physics
- South University of Science and Technology of China
- Shenzhen 518055
- China
| | - W. P. Xu
- Department of Physics
- South University of Science and Technology of China
- Shenzhen 518055
- China
| | - J. F. Liu
- Department of Physics
- South University of Science and Technology of China
- Shenzhen 518055
- China
| | - H. Xu
- Department of Physics
- South University of Science and Technology of China
- Shenzhen 518055
- China
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3
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Kang CJ, Denlinger JD, Allen JW, Min CH, Reinert F, Kang BY, Cho BK, Kang JS, Shim JH, Min BI. Electronic Structure of YbB_{6}: Is it a Topological Insulator or Not? PHYSICAL REVIEW LETTERS 2016; 116:116401. [PMID: 27035312 DOI: 10.1103/physrevlett.116.116401] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2015] [Indexed: 06/05/2023]
Abstract
To finally resolve the controversial issue of whether or not the electronic structure of YbB_{6} is nontrivially topological, we have made a combined study using angle-resolved photoemission spectroscopy (ARPES) of the nonpolar (110) surface and density functional theory (DFT). The flat-band conditions of the (110) ARPES avoid the strong band bending effects of the polar (001) surface and definitively show that YbB_{6} has a topologically trivial B 2p-Yb 5d semiconductor band gap of ∼0.3 eV. Accurate determination of the low energy band topology in DFT requires the use of a modified Becke-Johnson exchange potential incorporating spin-orbit coupling and an on-site Yb 4f Coulomb interaction U as large as 7 eV. The DFT result, confirmed by a more precise GW band calculation, is similar to that of a small gap non-Kondo nontopological semiconductor. Additionally, the pressure-dependent electronic structure of YbB_{6} is investigated theoretically and found to transform into a p-d overlap semimetal with small Yb mixed valency.
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Affiliation(s)
- Chang-Jong Kang
- Department of Physics, PCTP, Pohang University of Science and Technology, (POSTECH) Pohang 37673, Korea
| | - J D Denlinger
- Advanced Light Source, Lawrence Berkeley Laboratory, Berkeley, California 94720, USA
| | - J W Allen
- Department of Physics, Randall Laboratory, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Chul-Hee Min
- Universität Würzburg, Experimentelle Physik VII, 97074 Würzburg, Germany
| | - F Reinert
- Universität Würzburg, Experimentelle Physik VII, 97074 Würzburg, Germany
| | - B Y Kang
- School of Materials Science and Engineering, GIST, Gwangju 61005, Korea
| | - B K Cho
- School of Materials Science and Engineering, GIST, Gwangju 61005, Korea
| | - J-S Kang
- Department of Physics, The Catholic University of Korea, Bucheon 14662, Korea
| | - J H Shim
- Department of Physics, PCTP, Pohang University of Science and Technology, (POSTECH) Pohang 37673, Korea
- Department of Chemistry and Division of Advanced Nuclear Engineering, POSTECH, Pohang 37673, Korea
| | - B I Min
- Department of Physics, PCTP, Pohang University of Science and Technology, (POSTECH) Pohang 37673, Korea
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4
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Jayanthi Rajan K, Mohan Rao M, Satyanarayana L, Manivel Raja M, Mohan Kumar K, Srikanth VVSS, Subramanian M, Anandan C, Manorama SV. Luminescence and high temperature ferromagnetism in YAlO nanophosphors: materials for efficient next generation LEDs and spintronic applications. RSC Adv 2016. [DOI: 10.1039/c6ra01425a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Yttrium-aluminium-oxide (YAlO) based nanophosphors for environment friendly and efficient white LEDs and spintronics devices.
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Affiliation(s)
- K. Jayanthi Rajan
- Nanomaterials Laboratory
- Inorganic and Physical Chemistry Division
- CSIR-Indian Institute of Chemical Technology
- Hyderabad 500007
- India
| | - M. Mohan Rao
- Nanomaterials Laboratory
- Inorganic and Physical Chemistry Division
- CSIR-Indian Institute of Chemical Technology
- Hyderabad 500007
- India
| | - L. Satyanarayana
- Nanomaterials Laboratory
- Inorganic and Physical Chemistry Division
- CSIR-Indian Institute of Chemical Technology
- Hyderabad 500007
- India
| | - M. Manivel Raja
- Defence Metallurgical Research Laboratory
- Hyderabad 500058
- India
| | - Kuntumalla Mohan Kumar
- School of Engineering Sciences and Technology
- University of Hyderabad
- Hyderabad 500046
- India
| | | | - Munisamy Subramanian
- Department of Frontier Materials
- Graduate School of Engineering
- Nagoya Institute of Technology
- Nagoya 4668555
- Japan
| | - C. Anandan
- Surface Engineering Division
- National Aerospace Laboratories
- Bangalore 560017
- India
| | - Sunkara V. Manorama
- Nanomaterials Laboratory
- Inorganic and Physical Chemistry Division
- CSIR-Indian Institute of Chemical Technology
- Hyderabad 500007
- India
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5
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Huang B. Energy harvesting and conversion mechanisms for intrinsic upconverted mechano-persistent luminescence in CaZnOS. Phys Chem Chem Phys 2016; 18:25946-25974. [DOI: 10.1039/c6cp04706h] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Vacancy defects acting as native activators, e.g. V2+ZnO and V2+CaZnOS, function as energy conversion centers to transfer energy into photons.
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Affiliation(s)
- Bolong Huang
- Department of Applied Biology and Chemical Technology
- The Hong Kong Polytechnic University
- Kowloon
- China
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6
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Li X, Huang X, Duan D, Wu G, Liu M, Zhuang Q, Wei S, Huang Y, Li F, Zhou Q, Liu B, Cui T. The stability of B6 octahedron in BaB6 under high pressure. RSC Adv 2016. [DOI: 10.1039/c5ra23740h] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We have performed in situ synchrotron X-ray diffraction and first-principles calculations to explore the compression behavior of barium hexaboride (BaB6) under high pressure.
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7
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Huang B. Native Point Defects in CaS: Focus on Intrinsic Defects and Rare Earth Ion Dopant Levels for Up-converted Persistent Luminescence. Inorg Chem 2015; 54:11423-40. [DOI: 10.1021/acs.inorgchem.5b02061] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Bolong Huang
- Department of Physics and Materials Science, City University of Hong Kong, Kowloon, Hong Kong SAR, China
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8
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Jiang X, Zhao J. Evolution of boron clusters in iron tetraborides under high pressure: semiconducting and ferromagnetic superhard materials. RSC Adv 2015. [DOI: 10.1039/c5ra05852j] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The building block of the FeB4 compound transforms from a corrugated B6 ring to an unusual B4 tetrahedron and finally to a cubooctahedral B12 cluster under pressure. The latter two are predicted as superhard semiconductor or superhard magnetic materials.
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Affiliation(s)
- Xue Jiang
- Key Laboratory of Materials Modification by Laser
- Ion and Electron Beams (Dalian University of Technology)
- Ministry of Education
- Dalian 116024
- China
| | - Jijun Zhao
- Key Laboratory of Materials Modification by Laser
- Ion and Electron Beams (Dalian University of Technology)
- Ministry of Education
- Dalian 116024
- China
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9
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Wang H, LeBlanc KA, Gao B, Yao Y. Thermodynamic ground state of MgB6 predicted from first principles structure search methods. J Chem Phys 2014; 140:044710. [DOI: 10.1063/1.4862831] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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10
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Popov I, Baadji N, Sanvito S. Magnetism and antiferroelectricity in MgB6. PHYSICAL REVIEW LETTERS 2012; 108:107205. [PMID: 22463451 DOI: 10.1103/physrevlett.108.107205] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Indexed: 05/31/2023]
Abstract
We report on a density functional theory study demonstrating the coexistence of weak ferromagnetism and antiferroelectricity in boron-deficient MgB6. A boron vacancy produces an almost one dimensional extended molecular orbital, which is responsible for the magnetic moment formation. Then, long-range magnetic order can emerge from the overlap of such orbitals above percolation threshold. Although there is a finite density of states at the Fermi level, the localized nature of the charge density causes an inefficient electron screening. We find that the Mg2+ ions can displace from the center of their cubic cage, thus generating electrical dipoles. In the ground state these order in an antiferroelectric configuration. If proved experimentally, this will be the first material without d or f electrons displaying the coexistence of magnetic and electric order.
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Affiliation(s)
- Igor Popov
- School of Physics and CRANN, Trinity College, Dublin 2, Ireland
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11
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Ren S, Wuttig M. Organic exciton multiferroics. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2012; 24:724-727. [PMID: 22213111 DOI: 10.1002/adma.201104250] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2011] [Indexed: 05/31/2023]
Affiliation(s)
- Shenqiang Ren
- Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, USA.
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12
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Albert B, Hillebrecht H. Bor - elementare Herausforderung für Experimentatoren und Theoretiker. Angew Chem Int Ed Engl 2009. [DOI: 10.1002/ange.200903246] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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13
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Albert B, Hillebrecht H. Boron: Elementary Challenge for Experimenters and Theoreticians. Angew Chem Int Ed Engl 2009; 48:8640-68. [DOI: 10.1002/anie.200903246] [Citation(s) in RCA: 440] [Impact Index Per Article: 29.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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14
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Jash P, Trenary M. Synthesis of crystalline boron nanoribbons and calcium hexaboride nanowires by low pressure chemical vapor deposition. ACTA ACUST UNITED AC 2009. [DOI: 10.1088/1742-6596/176/1/012011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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15
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Li Z, Li L, Wu L, Du S. Assembly of Novel 2D and 3D Heterometallic Sb
III
–Cu
I
Polymers Based on Antimony(III) Thiolates as Metallothiolato Ligands. Eur J Inorg Chem 2009. [DOI: 10.1002/ejic.200801032] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Zhi‐Hua Li
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fujian, Fuzhou 350002, P. R. China, Fax: +86‐591‐83709470
| | - Long‐Hua Li
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fujian, Fuzhou 350002, P. R. China, Fax: +86‐591‐83709470
| | - Li‐Ming Wu
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fujian, Fuzhou 350002, P. R. China, Fax: +86‐591‐83709470
| | - Shao‐Wu Du
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fujian, Fuzhou 350002, P. R. China, Fax: +86‐591‐83709470
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16
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Jash P, Nicholls AW, Ruoff RS, Trenary M. Synthesis and characterization of single-crystal strontium hexaboride nanowires. NANO LETTERS 2008; 8:3794-3798. [PMID: 18950235 DOI: 10.1021/nl8021225] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Catalyst-assisted growth of single-crystal strontium hexaboride (SrB6) nanowires was achieved by pyrolysis of diborane (B2H6) over SrO powders at 760-800 degrees C and 400 mTorr in a quartz tube furnace. Raman spectra demonstrate that the nanowires are SrB6, and transmission electron microscopy along with selected area diffraction indicate that the nanowires consist of single crystals with a preferred [001] growth direction. Electron energy loss data combined with the TEM images indicate that the nanowires consist of crystalline SrB 6 cores with a thin (1 to 2 nm) amorphous oxide shell. The nanowires have diameters of 10-50 nm and lengths of 1-10 microm.
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Affiliation(s)
- Panchatapa Jash
- Department of Chemistry, University of Illinois at Chicago, Chicago, Illinois 60607, USA
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17
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Yahia MB, Reckeweg O, Gautier R, Bauer J, Schleid T, Halet JF, Saillard JY. Can Undoped Calcium Tetraborides Exist? An Answer from the Comparison of Its Density Functional Theory Electronic Structure with that of Rare-Earth Metal Tetraboride. Inorg Chem 2008; 47:6137-43. [DOI: 10.1021/ic701967n] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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18
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Maiti K, Medicherla VRR, Patil S, Singh RS. Revelation of the role of impurities and conduction electron density in the high resolution photoemission study of ferromagnetic hexaborides. PHYSICAL REVIEW LETTERS 2007; 99:266401. [PMID: 18233591 DOI: 10.1103/physrevlett.99.266401] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2007] [Indexed: 05/25/2023]
Abstract
We investigate the temperature evolution of the electronic structure of ferromagnetic CaB6 using ultrahigh resolution photoemission spectroscopy; the electronic structure of paramagnetic LaB6 is used as a reference. High resolution spectra of CaB6 reveal a finite density of states at the Fermi level E(F) at all the temperatures and evidence of impurity induced localized features in the vicinity of E(F), which are absent in the spectra of LaB6. Analysis of the high resolution spectra suggests that disorder in the B sublattice inducing partial localization in the mobile electrons and low electron density at E(F) is important to achieve ferromagnetism in these systems.
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Affiliation(s)
- Kalobaran Maiti
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005, India.
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19
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Takeda M, Terui M, Takahashi N, Ueda N. Improvement of thermoelectric properties of alkaline-earth hexaborides. J SOLID STATE CHEM 2006. [DOI: 10.1016/j.jssc.2006.01.025] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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20
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Baranovskiy AE, Grechnev GE, Logosha AV, Svechkarev IV, Filippov VB, Shitsevalova NY, Żogał OJ, Eriksson O. Electronic spectra and magnetic properties of RB6, RB12 and RB2C2 borides. ACTA ACUST UNITED AC 2006. [DOI: 10.1002/pssc.200562489] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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22
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Ammar A, Ménétrier M, Villesuzanne A, Matar S, Chevalier B, Etourneau J, Villeneuve G, Rodríguez-Carvajal J, Koo HJ, Smirnov AI, Whangbo MH. Investigation of the Electronic and Structural Properties of Potassium Hexaboride, KB6, by Transport, Magnetic Susceptibility, EPR, and NMR Measurements, Temperature-Dependent Crystal Structure Determination, and Electronic Band Structure Calculations. Inorg Chem 2004; 43:4974-87. [PMID: 15285674 DOI: 10.1021/ic049444c] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The electronic and structural properties of potassium hexaboride, KB(6), were examined by transport, magnetic susceptibility, EPR, and NMR measurements, temperature-dependent crystal structure determination, and electronic band structure calculations. The valence bands of KB(6) are partially empty, but the electrical resistivity of KB(6) reveals that it is not a normal metal. The magnetic susceptibility as well as EPR and NMR measurements show the presence of localized electrons in KB(6). The EPR spectra of KB(6) have two peaks, a broad ( approximately 320 G) and a narrow (less than approximately 27 G) line width, and the temperature-dependence of the magnetic susceptibility of KB(6) exhibits a strong hysteresis below 70 K. The temperature-dependent crystal structure determination of KB(6) shows the occurrence of an unusual variation in the unit cell parameter hence supporting that the hysteresis of the magnetic susceptibility is a bulk phenomenon. The line width DeltaH(pp) of the broad EPR signal is independent of temperature and EPR frequency. This finding indicates that the line broadening results from the dipole-dipole interaction, and the spins responsible for the broad EPR peak has the average distance of approximately 1.0 nm. To explain these apparently puzzling properties, we examined a probable mechanism of electron localization in KB(6) and its implications.
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Affiliation(s)
- A Ammar
- Institut de Chimie de la Matière Condensée de Bordeaux, ICMCB-CNRS, 87 Avenue du Dr. A. Schweitzer, 33608 Pessac Cedex, France
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23
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Cai MQ, Yin Z, Zhang MS. Optical properties of strontium titanate by ab initio calculation within density functional theory. Chem Phys Lett 2004. [DOI: 10.1016/j.cplett.2004.02.095] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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24
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Shi L, Gu Y, Chen L, Yang Z, Ma J, Qian Y. Low Temperature Synthesis and Characterization of Cubic CaB6Ultrafine Powders. CHEM LETT 2003. [DOI: 10.1246/cl.2003.958] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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25
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Souma S, Komatsu H, Takahashi T, Kaji R, Sasaki T, Yokoo Y, Akimitsu J. Electronic band structure and Fermi surface of CaB6 studied by angle-resolved photoemission spectroscopy. PHYSICAL REVIEW LETTERS 2003; 90:027202. [PMID: 12570575 DOI: 10.1103/physrevlett.90.027202] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2002] [Indexed: 05/24/2023]
Abstract
We report high-resolution angle-resolved photoemission spectroscopy (ARPES) on CaB6. The band structure determined by ARPES shows a 1 eV energy gap at the X point between the valence and the conduction bands. We found a small electron pocket at the X point, whose carrier number is estimated to be (4-5) x 10(19) cm(-3), in good agreement with the Hall resistivity measurement with the same crystal. The experimental results are discussed in comparison with band structure calculations and theoretical models for the high-temperature ferromagnetism.
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Affiliation(s)
- S Souma
- Department of Physics, Tohoku University, Sendai 980-8578, Japan
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26
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Young DP, Fisk Z, Thompson JD, Ott HR, Oseroff SB, Goodrich RG. Parasitic ferromagnetism in a hexaboride? Nature 2002. [DOI: 10.1038/420144a] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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27
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Denlinger JD, Clack JA, Allen JW, Gweon GH, Poirier DM, Olson CG, Sarrao JL, Bianchi AD, Fisk Z. Bulk band gaps in divalent hexaborides. PHYSICAL REVIEW LETTERS 2002; 89:157601. [PMID: 12366022 DOI: 10.1103/physrevlett.89.157601] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2001] [Indexed: 05/23/2023]
Abstract
Complementary angle-resolved photoemission and bulk-sensitive k-resolved resonant inelastic x-ray scattering of divalent hexaborides reveal a >1 eV X-point gap between the valence and conduction bands, in contradiction to the band overlap assumed in several models of their novel ferromagnetism. This semiconducting gap implies that carriers detected in transport measurements arise from defects, and the measured location of the bulk Fermi level at the bottom of the conduction band implicates boron vacancies as the origin of the excess electrons. The measured band structure and X-point gap in CaB6 additionally provide a stringent test case for many-body quasiparticle band calculations.
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Affiliation(s)
- J D Denlinger
- Advanced Light Source, Lawrence Berkeley National Laboratory, California 94720, USA
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28
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Bascones E, Burkov AA, MacDonald AH. Theory of ferromagnetism in doped excitonic condensates. PHYSICAL REVIEW LETTERS 2002; 89:086401. [PMID: 12190486 DOI: 10.1103/physrevlett.89.086401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2001] [Indexed: 05/23/2023]
Abstract
Nesting in a semimetal can lead to an excitonic-insulator state with spontaneous coherence between conduction and valence bands and a gap for charged excitations. We present a theory of the ferromagnetic state that occurs when the density of electrons in the conduction band and holes in the valence band differ. We find an unexpectedly rich doping-field phase diagram and an unusual collective excitation spectrum that includes two gapless collective modes. We predict regions of doping and external field in which phase-separated condensates of electrons and holes with parallel spins and opposing spins coexist.
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Affiliation(s)
- E Bascones
- Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA
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Murakami S, Shindou R, Nagaosa N, Mishchenko AS. Theory of ferromagnetism in Ca(1-x)La(x)B(6). PHYSICAL REVIEW LETTERS 2002; 88:126404. [PMID: 11909486 DOI: 10.1103/physrevlett.88.126404] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2001] [Indexed: 05/23/2023]
Abstract
Novel ferromagnetism in Ca(1-x)La(x)B(6) is studied in terms of the Ginzburg-Landau theory for excitonic-order parameters, taking into account symmetry of the wave functions. We found that the minima of the free energy break both inversion and time-reversal symmetries, while the product of these two remains preserved. This explains various novelties of the ferromagnetism and predicts a number of magnetic properties, including the magnetoelectric effect, which can be tested experimentally.
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Affiliation(s)
- Shuichi Murakami
- Department of Applied Physics, University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan.
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Wolf SA, Awschalom DD, Buhrman RA, Daughton JM, von Molnár S, Roukes ML, Chtchelkanova AY, Treger DM. Spintronics: a spin-based electronics vision for the future. Science 2001; 294:1488-95. [PMID: 11711666 DOI: 10.1126/science.1065389] [Citation(s) in RCA: 1995] [Impact Index Per Article: 86.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
This review describes a new paradigm of electronics based on the spin degree of freedom of the electron. Either adding the spin degree of freedom to conventional charge-based electronic devices or using the spin alone has the potential advantages of nonvolatility, increased data processing speed, decreased electric power consumption, and increased integration densities compared with conventional semiconductor devices. To successfully incorporate spins into existing semiconductor technology, one has to resolve technical issues such as efficient injection, transport, control and manipulation, and detection of spin polarization as well as spin-polarized currents. Recent advances in new materials engineering hold the promise of realizing spintronic devices in the near future. We review the current state of the spin-based devices, efforts in new materials fabrication, issues in spin transport, and optical spin manipulation.
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Affiliation(s)
- S A Wolf
- Defense Advanced Research Projects Agency (DARPA), 3701 North Fairfax Drive, Arlington, VA 22203, USA.
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Monnier R, Delley B. Point defects, ferromagnetism, and transport in calcium hexaboride. PHYSICAL REVIEW LETTERS 2001; 87:157204. [PMID: 11580724 DOI: 10.1103/physrevlett.87.157204] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2001] [Indexed: 05/23/2023]
Abstract
The formation energy and local magnetic moment of a series of point defects in CaB6 are computed using a supercell approach within the generalized gradient approximation to density functional theory. It is found that the substitution of Ca by La does not lead to the formation of a local moment, while a neutral B6 vacancy carries a moment of 2.4 Bohr magnetons. A plausible mechanism for the ferromagnetic ordering of these moments is suggested. Since the same broken B-B bonds appear on the preferred (100) cleavage planes of the CaB6 structure, it is argued that internal surfaces in polycrystals as well as external surfaces in general will make a large contribution to the observed magnetization.
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Affiliation(s)
- R Monnier
- Laboratorium für Festkörperphysik, ETH-Hönggerberg, CH-8093 Zürich, Switzerland
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Akimitsu J, Takenawa K, Suzuki K, Harima H, Kuramoto Y. High-temperature ferromagnetism in CaB2C2. Science 2001; 293:1125-7. [PMID: 11498587 DOI: 10.1126/science.1061501] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
We report a high Curie-temperature ferromagnet, CaB2C2. Although the compound has neither transition metal nor rare earth ions, the ferromagnetic transition temperature Tc is about 770 Kelvin. Despite this high T(c), the magnitude of the ordered moment at room temperatures is on the order of 10(-4) Bohr magneton per formula unit. These properties are rather similar to those of doped divalent hexaborides, such as Ca(1-x)La(x)B6. The calculated electronic states also show similarity near the Fermi level between CaB2C2 and divalent hexaborides. However, there is an important difference: CaB2C2 crystallizes in a tetragonal structure, and there are no equivalent pockets in the energy bands for electrons and holes-in contrast with CaB6. Thus, the disputed threefold degeneracy, specific to the cubic structure, in the energy bands of divalent hexaborides turns out not to be essential for high-temperature ferromagnetism. It is the peculiar molecular orbitals near the Fermi level that appear to be crucial to the high-Tc ferromagnetism.
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Affiliation(s)
- J Akimitsu
- Department of Physics, Aoyama-Gakuin University, Tokyo 157-8572, Japan.
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