Quantum matter in high magnetic fields

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Evolution of the Fermi surface of BaFe_2(As_{1-x}P_x)_2 on entering the superconducting dome

(2009)

Authors:

H Shishido, AF Bangura, AI Coldea, S Tonegawa, K Hashimoto, S Kasahara, PMC Rourke, H Ikeda, T Terashima, R Settai, Y Onuki, D Vignolles, C Proust, B Vignolle, A McCollam, Y Matsuda, T Shibauchi, A Carrington
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Interplay between localized and itinerant d electrons in a frustrated metallic antiferromagnet, 2H-AgNiO2

(2009)

Authors:

AI Coldea, A Carrington, R Coldea, L Malone, AF Bangura, MD Johannes, II Mazin, EA Yelland, JG Analytis, JAAJ Perenboom, C Jaudet, D Vignolles, T Sorgel, M Jansen
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Interplay between localized and itinerant d electrons in a frustrated metallic antiferromagnet, 2H-AgNiO2

ArXiv 0908.4169 (2009)

Authors:

AI Coldea, A Carrington, R Coldea, L Malone, AF Bangura, MD Johannes, II Mazin, EA Yelland, JG Analytis, JAAJ Perenboom, C Jaudet, D Vignolles, T Sorgel, M Jansen

Abstract:

We report the electronic and magnetic behaviour of the frustrated triangular metallic antiferromagnet 2H-AgNiO2 in high magnetic fields (54 T) using thermodynamic and transport measurements. Here localized d electrons are arranged on an antiferromagnetic triangular lattice nested inside a honeycomb lattice with itinerant d electrons. When the magnetic field is along the easy axis we observe a cascade of field-induced transitions, attributed to the competition between easy-axis anisotropy, geometrical frustration and coupling of the localized and itinerant system. The quantum oscillations data suggest that the Fermi surface is reconstructed by the magnetic order but in high fields magnetic breakdown orbits are possible. The itinerant electrons are extremely sensitive to scattering by spin fluctuations and a significant mass enhancement (~ 3) is found.
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Fermi surface of SrFe2P2 determined by the de Haas-van Alphen effect.

Phys Rev Lett 103:7 (2009) 076401

Authors:

JG Analytis, CMJ Andrew, AI Coldea, A McCollam, J-H Chu, RD McDonald, IR Fisher, A Carrington

Abstract:

We report measurements of the Fermi surface (FS) of the ternary iron-phosphide SrFe2P2 using the de Haas-van Alphen effect. The calculated FS of this compound is very similar to SrFe2As2, the parent compound of the high temperature superconductors. Our data show that the Fermi surface is composed of two electron and two hole sheets in agreement with band-structure calculations. Several of the sheets show strong c-axis warping emphasizing the importance of three dimensionality in the nonmagnetic state of the ternary pnictides. We find that the electron and hole pockets have a different topology, implying that this material does not satisfy a (pi, pi) nesting condition.
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Topological change of the Fermi surface in ternary iron pnictides with reduced c/a ratio: a de Haas-van Alphen study of CaFe2P2.

Phys Rev Lett 103:2 (2009) 026404

Authors:

Amalia I Coldea, CMJ Andrew, JG Analytis, RD McDonald, AF Bangura, J-H Chu, IR Fisher, A Carrington

Abstract:

We report a de Haas-van Alphen effect study of the Fermi surface of CaFe2P2 using low-temperature torque magnetometry up to 45 T. This system is a close structural analog of the collapsed tetragonal nonmagnetic phase of CaFe2As2. We find the Fermi surface of CaFe2P2 to differ from other related ternary phosphides in that its topology is highly dispersive in the c axis, being three dimensional in character and with identical mass enhancement on both electron and hole pockets ( approximately 1.5). This suggests that when the bonding between pnictogen layers becomes important nesting conditions are not fulfilled.
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