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Helm T, Valdivia PN, Bourret-Courchesne E, Analytis JG, Birgeneau RJ. The influence of magnetic order on the magnetoresistance anisotropy of Fe 1 + δ-x Cu x Te. J Phys Condens Matter 2017; 29:285801. [PMID: 28513476 DOI: 10.1088/1361-648x/aa73c1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We performed resistance measurements on [Formula: see text]Cu x Te with [Formula: see text] in the presence of in-plane applied magnetic fields, revealing a resistance anisotropy that can be induced at a temperature far below the structural and magnetic zero-field transition temperatures. The observed resistance anisotropy strongly depends on the field orientation with respect to the crystallographic axes, as well as on the field-cooling history. Our results imply a correlation between the observed features and the low-temperature magnetic order. Hysteresis in the angle-dependence indicates a strong pinning of the magnetic order within a temperature range that varies with the Cu content. The resistance anisotropy vanishes at different temperatures depending on whether an external magnetic field or a remnant field is present: the closing temperature is higher in the presence of an external field. For [Formula: see text] the resistance anisotropy closes above the structural transition, at the same temperature at which the zero-field short-range magnetic order disappears and the sample becomes paramagnetic. Thus we suggest that under an external magnetic field the resistance anisotropy mirrors the magnetic order parameter. We discuss similarities to nematic order observed in other iron pnictide materials.
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Affiliation(s)
- T Helm
- Department of Physics, University of California, Berkeley, CA 94720, United States of America. Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States of America. Present address: Max Planck Institute for Chemical Physics of Solids, Noethnitzer Str. 40, 01187 Dresden, Germany
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Forrest TR, Valdivia PN, Rotundu CR, Bourret-Courchesne E, Birgeneau RJ. The effects of post-growth annealing on the structural and magnetic properties of BaFe2As2. J Phys Condens Matter 2016; 28:115702. [PMID: 26895292 DOI: 10.1088/0953-8984/28/11/115702] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We investigate the effects of post-growth annealing on the structural and magnetic properties of BaFe2As2. Magnetic susceptibility measurements, which exhibit a signal corresponding to the magnetic phase transition, and high-resolution x-ray diffraction measurements, which directly probe the structural order parameter, show that annealing causes the ordering temperatures of both the phase transitions to increase, sharpen and converge. In the as grown sample, our measurements show two distinct transitions corresponding to structural and magnetic ordering, which are separated in temperature by approximately 1 K. After 46 days (d) of annealing at 700 °C, the two become concurrent in temperature. These measurements demonstrate that the structural phase transition is second-order like when the magnetic and structural phase transitions are separated in temperature, and first-order like when the two phase transition temperatures coincide. This observation indicates that annealing causes the system to cross a hitherto undiscovered tricritical point. In addition, x-ray diffraction measurements show that the c-axis lattice parameter increases with annealing up to 30 d, but remains constant for longer annealing times. Comparisons of BaFe2As2 to SrFe2As2 are made when possible.
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Affiliation(s)
- T R Forrest
- Department of Physics, University of California, Berkeley, CA 94720, USA
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Yi M, Wang M, Kemper AF, Mo SK, Hussain Z, Bourret-Courchesne E, Lanzara A, Hashimoto M, Lu DH, Shen ZX, Birgeneau RJ. Bandwidth and Electron Correlation-Tuned Superconductivity in Rb_{0.8}Fe_{2}(Se_{1-z}S_{z})_{2}. Phys Rev Lett 2015; 115:256403. [PMID: 26722933 DOI: 10.1103/physrevlett.115.256403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Indexed: 06/05/2023]
Abstract
We present a systematic angle-resolved photoemission spectroscopy study of the substitution dependence of the electronic structure of Rb_{0.8}Fe_{2}(Se_{1-z}S_{z})_{2} (z=0, 0.5, 1), where superconductivity is continuously suppressed into a metallic phase. Going from the nonsuperconducting Rb_{0.8}Fe_{2}S_{2} to superconducting Rb_{0.8}Fe_{2}Se_{2}, we observe little change of the Fermi surface topology, but a reduction of the overall bandwidth by a factor of 2. Hence, for these heavily electron-doped iron chalcogenides, we have identified electron correlation as explicitly manifested in the quasiparticle bandwidth to be the important tuning parameter for superconductivity, and that moderate correlation is essential to achieving high T_{C}.
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Affiliation(s)
- M Yi
- Department of Physics, University of California Berkeley, Berkeley, California 94720, USA
| | - Meng Wang
- Department of Physics, University of California Berkeley, Berkeley, California 94720, USA
| | - A F Kemper
- Computational Research Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - S-K Mo
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Z Hussain
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - E Bourret-Courchesne
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - A Lanzara
- Department of Physics, University of California Berkeley, Berkeley, California 94720, USA
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - M Hashimoto
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - D H Lu
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - Z-X Shen
- Stanford Institute of Materials and Energy Sciences, Stanford University, Stanford, California 94305, USA
- Departments of Physics and Applied Physics, and Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA
| | - R J Birgeneau
- Department of Physics, University of California Berkeley, Berkeley, California 94720, USA
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA
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Zhao J, Rotundu CR, Marty K, Matsuda M, Zhao Y, Setty C, Bourret-Courchesne E, Hu J, Birgeneau RJ. Effect of electron correlations on magnetic excitations in the isovalently doped iron-based superconductor Ba(Fe(1-x)Ru(x))(2)As(2). Phys Rev Lett 2013; 110:147003. [PMID: 25167027 DOI: 10.1103/physrevlett.110.147003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2012] [Indexed: 06/03/2023]
Abstract
Magnetic correlations in isovalently doped Ba(Fe(1-x)Ru(x))(2)As(2) (x = 0.25, T(c) = 14.5 K; x = 0.35, T(c) = 20 K) are studied by elastic and inelastic neutron scattering techniques. A relatively large superconducting spin gap accompanied by a weak resonance mode is observed in the superconducting state in both samples. In the normal state, the magnetic excitation intensity is dramatically reduced with increasing Ru doping toward the optimally doped regime. Our results favor that the weakening of the electron-electron correlations by Ru doping is responsible for the dampening of the resonance mode, as well as the suppression of the normal state antiferromagnetic correlations near the optimally doped regime in this system.
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Affiliation(s)
- Jun Zhao
- Department of Physics, and Laboratory of Advanced Materials, State Key Laboratory of Surface Physics, Fudan University, Shanghai 200433, People's Republic of China and Department of Physics, University of California, Berkeley, California 94720, USA and Miller Institute for Basic Research in Science, Berkeley, California 94720, USA
| | - C R Rotundu
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - K Marty
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - M Matsuda
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Y Zhao
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA and Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, USA
| | - C Setty
- Department of Physics, Purdue University, West Lafayette, Indiana 47907, USA
| | - E Bourret-Courchesne
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Jiangping Hu
- Department of Physics, Purdue University, West Lafayette, Indiana 47907, USA
| | - R J Birgeneau
- Department of Physics, University of California, Berkeley, California 94720, USA and Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA
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Zhao J, Cao H, Bourret-Courchesne E, Lee DH, Birgeneau RJ. Neutron-diffraction measurements of an antiferromagnetic semiconducting phase in the vicinity of the high-temperature superconducting state of K(x)Fe(2-y)Se2. Phys Rev Lett 2012; 109:267003. [PMID: 23368605 DOI: 10.1103/physrevlett.109.267003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Indexed: 06/01/2023]
Abstract
The recently discovered K-Fe-Se high-temperature superconductor has caused heated debate regarding the nature of its parent compound. Transport, angle-resolved photoemission spectroscopy, and STM measurements have suggested that its parent compound could be insulating, semiconducting, or even metallic [M. H. Fang, H.-D. Wang, C.-H. Dong, Z.-J. Li, C.-M. Feng, J. Chen, and H. Q. Yuan, Europhys. Lett. 94, 27009 (2011); F. Chen et al., Phys. Rev. X 1, 021020 (2011); and W. Li et al., Phys. Rev. Lett. 109, 057003 (2012)]. Because the magnetic ground states associated with these different phases have not yet been identified and the relationship between magnetism and superconductivity is not fully understood, the real parent compound of this system remains elusive. Here, we report neutron-diffraction experiments that reveal a semiconducting antiferromagnetic (AFM) phase with rhombus iron vacancy order. The magnetic order of the semiconducting phase is the same as the stripe AFM order of the iron pnictide parent compounds. Moreover, while the sqrt[5]×sqrt[5] block AFM phase coexists with superconductivity, the stripe AFM order is suppressed by it. This leads us to conjecture that the new semiconducting magnetic ordered phase is the true parent phase of this superconductor.
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Affiliation(s)
- Jun Zhao
- Department of Physics, University of California, Berkeley, California 94720, USA.
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