Spin texture on top of flux avalanches in Nb/Al2O3/Co thin film heterostructures

Abstract

We report on magneto-optical imaging, magnetization, Hall effect and magnetoresistance experiments in Nb/Al 2 O 3 /Co thin film heterostructures.The magnetic field is applied perpendicularly to the plane of the film and gives rise to abrupt flux penetration of dendritic form. A magnetization texture is imprinted in the Co layer in perfect coincidence with these ramifications. The spin domains that mimic the vortex dendrites are stable upon the field removal. Moreover, the imprinted spin structure remains visible up to room temperature. Complementary magnetization, Hall effect and magneto-resistance experiments were performed in a similar sample where electrical contacts were placed on the Co layer. In the region of the field -temperature diagram where flux instabilities are known to occur in Nb films, irregular jumps are observed in the magnetic hysteresis and large amplitude noise is detected in the magneto-resistance and Hall resistivity data when measured as a function of the field.

Magnetic Recording of Superconducting States

“…Similar imprinting of magnetic flux paths in a superconductor to generate unconventional spin textures in ferromagnetic layers has been reported in Nb/Al 2 O 3 /Co thin film heterostructures by Lopes and co-workers [57]. After zero field cooling the sample from above T c of Nb to T = 2.5 K, the magnetic flux is observed to penetrate in the form of several dendrite structures (cf.…”

“…Over the years, the technique has been utilized to various ends; achieving single vortex resolution [49,[52][53][54] and detecting large area phenomena such as flux avalanches in superconductors [55,56]. This technique has been successfully used [56,57] to trace flux trajectories in superconductors by magnetic imprinting.…”

“…Moreover, it is estimated that the magnetic energy provided by the flux front in Nb to the Co film may not be sufficient to induce spin-flipping [77]. Rather than that, it is speculated in Reference [57] that, at the microscopic scale, the observed magnetization texture could result from the formation of skyrmions or some other non-conventional spin chiral-type or vortex-type structures.…”

Controlling magnetic flux penetration in low-T C superconducting films and hybrids

“…One then has a valuable setup to study and optimize the effects of the mutual presence of both layers. Recent studies [6,[48][49][50][51][52][53] have revealed that one can use the magnetic state of a ferromagnetic layer to tailor vortex dynamics in the superconducting film. Conversely, it was also demonstrated that the vortex movement can alter the magnetic state of a ferromagnetic layer, which keeps a magnetic record of the tracks left behind by moving magnetic flux [48,52,54].…”

Dynamics and heat diffusion of Abrikosov’s vortex-antivortex pairs during an annihilation process

“…The study of vortex matter is an issue of greatest interest, since the comprehension and manipulation of the vortex motion are very important for possible applications as in the case of control of spins by vortices [1][2][3]. However, unusual behaviors appear when the vortices are subjected to an environment where the confinement effects emerge, as is the case of mesoscopic systems.…”