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Hysteresis loops of magnetoconductance in graphene devices

A. Candini, C. Alvino, W. Wernsdorfer, and M. Affronte
Phys. Rev. B 83, 121401(R) – Published 3 March 2011
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Abstract

We report very low-temperature magnetoconductance ΔG measurements on graphene devices with the magnetic field H applied parallel to the carbon sheet. The ΔG(H) signal depends on the gate voltage Vg and its sign is related to the universal conductance fluctuations. When the magnetic field is swept at fast rates, ΔG displays hysteresis loops evident for different sizes and at different transport regimes of the devices. We attribute this to the magnetization reversal of paramagnetic centers in the graphene layer, which might originate from defects in our devices.

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  • Received 9 December 2010

DOI:https://doi.org/10.1103/PhysRevB.83.121401

©2011 American Physical Society

Authors & Affiliations

A. Candini1,3,*, C. Alvino1,2, W. Wernsdorfer3, and M. Affronte1,2

  • 1S3, Istituto Nanoscienze - CNR, via Campi 213/a, I-41125 Modena, Italy
  • 2Dipartimento di Fisica, Università di Modena e Reggio Emilia, via Campi 213/a, I-41125 Modena, Italy
  • 3Institut Néel, CNRS, BP166, 25 Avenue des Martyrs, F-38042 Grenoble, France

  • *andrea.candini@nano.cnr.it

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Vol. 83, Iss. 12 — 15 March 2011

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  • Figure 1
    Figure 1
    Source-drain conductance for varying back-gate voltage at 0.04 K. Inset: False-color scanning electron microscope picture of the nanoconstriction presented in the text. The graphene layer has been colored light green (gray) to enhance the contrast; the dark regions correspond to the substrate after O2 plasma etching of graphene. Source and drain part of graphene are indicated.Reuse & Permissions
  • Figure 2
    Figure 2
    Parallel magnetoconductance of the devices at three different gate voltages. All measurements have been performed at 0.04 K sweeping the magnetic field at a rate of 0.05 T/s. The curves have been selected to show that the magnetoconductance can be positive (a), negative (b), or flat (c). In the (a) and (b) cases, a hysteresis is observed.Reuse & Permissions
  • Figure 3
    Figure 3
    (a) Color scale plot of the hysteresis δG (defined as the difference between the curve recorded while upsweeping the magnetic field and the curve recorded while the field is ramped back) vs gate voltage. (b) Corresponding zero-field conductance for the same gate region. δG is maximum in correspondence of a maximum or a minimum in G(Vg) and its sign is reversed between them.Reuse & Permissions
  • Figure 4
    Figure 4
    (a) Hysteresis loops obtained for different field sweeping rates at base temperature. The loop is strongly rate dependent and it disappears for slow sweeping rates. (b) Evolution of the magnetoconductance curves as a function of temperature sweeping the field at 0.05 T/s. The hysteresis loop is still present up to ~1 K, becoming undetectable when the magnetoconductance signal is flat and dominated by noise.Reuse & Permissions
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