Magnetic susceptibility of YBa2Cu3O6+x crystals : Unusual Curie behavior and small contributions from charge density waves

Kokanović, Ivan and Cooper, J. R. (2016) Magnetic susceptibility of YBa2Cu3O6+x crystals : Unusual Curie behavior and small contributions from charge density waves. Physical Review B, 94 (7). pp. 75155-11. ISSN 1098-0121

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Abstract

We report measurements of the magnetic susceptibility of twinned single crystals of YBa2Cu3O6+x from just above their superconducting transition temperatures to 300 K with magnetic fields of up to 5 T applied parallel and perpendicular to the CuO2 planes at seven values of x. Appropriate analysis allows the relatively small, but still important, Curie terms to be separated from other contributions to the susceptibility. Our data support a picture in which the Curie terms arise from oxygen disorder in the Cu-O chains. This agrees with published work on polycrystalline samples where the sample cooling rate was varied, but here we show that the Curie plots flatten out above 200 K. We identify small effects of charge density wave (CDW) instabilities in the temperature (T ) derivative of the in-plane susceptibility dχab(T)/dT and discuss their x dependence. For x = 0.67 we make a detailed comparison with published high energy x-ray diffraction data using a minimal model involving Fermi arcs, thereby obtaining values for the CDW energy gap and the Helmholtz free energy in a coherence volume. At 80 and 100 K the latter is comparable with, or smaller than, kBT , respectively, highlighting the probable importance of thermal fluctuations. We note that the effect of the Lorentz force on charge carriers in the Fermi arcs could provide a simple mechanism for enhancing the CDWs in high magnetic fields, as suggested by recent experiments.

Item Type: Article
Date: 29 August 2016
Subjects: NATURAL SCIENCES > Physics
Additional Information: © 2016 American Physical Society. Received 23 June 2016; revised manuscript received 25 July 2016; published 29 August 2016.
Divisions: Faculty of Science > Department of Physics
Publisher: American Physical Society
Depositing User: Gordana Stubičan Ladešić
Date Deposited: 12 Sep 2016 11:16
Last Modified: 29 Nov 2017 16:41
URI: http://digre.pmf.unizg.hr/id/eprint/5048

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