Guided vortex motion in superconductors with a square antidot array

Abstract

We have measured the in-plane anisotropy of the vortex mobility in a thin Pb film with a square array of antidots. The Lorentz force, acting on the vortices, was rotated by adding two perpendicular currents and keeping the amplitude of the net current constant. One set of voltage probes was used to detect the vortex motion. We show that the pinning landscape provided by the square antidot lattice influences the vortex motion in two different ways. First, the modulus of the vortex velocity becomes angular dependent with a lower mobility along the diagonals of the pinning array. Second, the vortex displacement is preferentially parallel to the principal axes of the underlying pinning lattice, giving rise to a misalignment between the vortex velocity and the applied Lorentz force. We show that this anisotropic vortex motion is temperature dependent and progressively fades out when approaching the normal state.

Switchable magnetic dipole induced guided vortex motion

“…In order to unveil the lattice symmetry contribution we can assume that each dipole behaves as an effective isotropic pinning center, very much like a lattice of circular antidots or magnetic dots. In this case it has been previously shown [10] that the minimum pinning force is along the principal axes of the pinning lattice [broken line in Fig.1(c) and (d)]. On the other hand, ignoring the presence of the lattice and just considering the pinning force produced by one single dipole gives rise to a strongly anisotropic pinning force [25] [schematically displayed as an off-centered circle in Fig.1(c) and (d)].…”

“…These systems rely essentially on either static arrays, such as pinning centers [2,3,4,5] and vortex-antivortex generators [6,7], or components influencing the vortex dynamics like channels [8,9,10,11] and ratchets [12,13]. The ultimate motivation behind the manipulation of the local vortex density is to enhance the performance of superconductor-based devices by reducing the noise in squid-based systems [14,15], gaining control on superconducting THz emitters [16] or even providing a way to predefine the optical transmission through the system [17].…”

The effect of nanoscale Fe doping on the superconducting properties of MgB2

“…Recently, Prozorov et al applied a sonication method to produce magnetic Fe 2 O 3 nanoparticles embedded in the MgB 2 bulk, resulting in a superconductor-ferromagnetic composite which exhibited enhancement of the magnetic hysteresis due to the improved vortex pinning by the magnetic nanoparticles [4]. In conventional superconductors, submicron magnetic dots in a specially designed pattern have been used as artificial pinning centers in superconductor thin films [5,6]. Because of the important role of Fe as a commonly used sheath material for the fabrication of MgB 2 there is an urgent need to clarify the effects of Fe doping on the superconducting properties, in particular on the flux pinning.…”

Enhanced pinning and proliferation of matching effects in a superconducting film with a Penrose array of magnetic dots

“…However, at high temperatures these commensurability effects occur only in a very narrow window of fields [2]. Moreover, for particular current orientations the periodic pinning might also promote an undesired channeling of vortices [3,4]. In principle, these limitations could be prevented by introducing a random distribution of pinning centers at expenses of loosing the majority of the matching features [5,6].…”