K. Vervaeke

University of Leuven, Louvain, Flanders, Belgium

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Publications (4)12.47 Total impact

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    ABSTRACT: In this paper the magnetic field detection limits of microscopic Hall sensors are investigated as a function of their lateral size. Hall sensors fabricated from GaAs/AlGaAs heterostructures and silicon are experimentally investigated at different temperatures using Hall effect and noise spectrum measurements. At room temperature a clear size dependence of the detection limit is observed, whereas at low temperatures this dependence is found to disappear. The results are explained using the theory of noise in semiconductors.
    The Review of scientific instruments 08/2009; 80(7):074701. · 1.52 Impact Factor
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    ABSTRACT: Ballistic Hall magnetometry is used to investigate the magnetization of a mesoscopic superconducting Pb square as a function of magnetic field (H) and temperature (T). Vortex penetration and expulsion fields are determined from magnetization curves at different temperatures below Tc and are combined in an experimental T-H phase diagram. Enhanced stability of the symmetry-matching vorticities L=1 and L=4 is observed. The experimental results are compared with theoretical calculations using the nonlinear Ginzburg-Landau theory for a thin square.
    Physical review. B, Condensed matter 11/2007; 76(18). · 3.77 Impact Factor
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    ABSTRACT: Inhomogeneous magnetic fields generated by the BaFe12O19 ferromagnetic substrate create a magnetic template for superconducting condensate in the Nb/BaFe12O19 hybrids. Depending on the field and temperature, the magnetic template guides superconductivity to nucleate in different areas: above the magnetic domain walls of the BaFe12O19 forming the domain-wall superconductivity (DWS), above the reversed magnetic domains (RDS), and above the positive magnetic domains forming bulk superconductivity. The DWS, behaving as a superconducting wire network, survives in a broad field range. The RDS, existing in the form of isolated superconducting islands near the saturation field Hs of BaFe12O19 , can be described as a two-dimensional two-component random conductor mixture. Being related to the hysteretic domain evolution, superconducting condensate above the reversed domains shows pronounced switching behavior.
    Physical Review B 06/2006; · 3.66 Impact Factor
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    ABSTRACT: The effect of the patterning of a Ga1-xMnxAs (x=0.08) film into an array of microscopic dots on its magnetic properties is locally studied by means of scanning Hall probe microscopy. The measured stray field patterns indicate the presence of a single domain state with a uniform magnetization within the Ga1-xMnxAs dots. The magnetic anisotropy of the dot array is directly imaged, revealing a [100] easy axis in the as-grown sample and a [110] easy axis orientation after annealing. In contrast to a temperature dependent anisotropy in the plain Ga1-xMnxAs film, no magnetic easy axis reorientation is observed within the experimentally accessible temperature range.
    Applied Physics Letters 01/2006; 89. · 3.52 Impact Factor