Ferromagnetic pinning arrays

Superconducting vortex pinning with artificial magnetic nanostructures

“…Different materials have been used for the fabrication of the magnetic nanostructures such as SmCo [11,48], Ni [25,49], Fe [50], or Co [51] and, also perpendicular anisotropy Co/Pd and Co/Pt multilayers [43,52].…”

“…Out of plane magnetized dots produce asymmetric pinning, which depends on the relative alignment between the dot magnetic moment and the applied magnetic field that creates the vortices in the superconductor [30,52]. Stronger maxima are observed in the critical current for a parallel than for an antiparallel alignment.…”

Driving force for commensurate vortex domain formation in periodic pinning arrays

“…Our experiments were performed on a 50 nm granular Pb film (T c ¼ 7:17 K) deposited over an a ¼ 1 lm period square array (H 1 ¼ U 0 =a 2 ¼ 20:67 Oe) of 0.4 lm square ferromagnetic ÔdotsÕ with perpendicular magnetic anisotropy patterned in a [Co(0.3 nm)/Pt(1.1 nm)] 10 multilayer film [5,7,15]. The overall array size was $2 mm · 2 mm and contained about 4 · 10 6 magnetic dots.…”

“…It is now well known that commensurate vortex structures form in these materials at certain specific values of the vortex density when sharp peaks in the bulk magnetisation and critical current are observed [1][2][3][4][5][6][7]. Many different types of artificial pinning object have been successfully realised including arrays of sub-micron holes (antidots) [1][2][3] or ferromagnetic dots with both in-plane [4,5] and perpendicular anisotropy [6,7], yet the qualitative features of the matching phenomena appear to be generic to all of these. The strongest critical current enhancements occur at integer matching fields, when one or more vortices become trapped at each pinning site.…”

Critical Currents and Melting Temperature of a Two-Dimensional Vortex Lattice with Periodic Pinning

“…When the vortex lattice is commensurate with the pinning array; that is, when the rate B/B Φ is an integer or a rational fraction, the critical current J c is strongly enhanced. These commensurability effects have been intensively studied [2][3][4][5][6][7][8][9], and they have been observed to reduce the vortex mobility and to help in increasing the critical current. In contrast, for samples where the external magnetic field is increased above the first matching field, some vortices will not be trapped at a pinning site.…”