Irreversible magnetization switching at the onset of superconductivity in a superconductor ferromagnet hybrid

Abstract

We demonstrate that the magnetic state of a superconducting spin valve, that is normally controlled with an external magnetic field, can also be manipulated by varying the temperature which increases the functionality and flexibility of such structures as switching elements. In this case, switching is driven by changes in the magnetostatic energy due to spontaneous Meissner screening currents forming in the superconductor below the critical temperature. Our scanning Hall probe measurements also reveal vortex-mediated pinning of the ferromagnetic domain structure due to the pinning of quantized stray fields in the adjacent superconductor. The ability to use temperature as well as magnetic field to control the local magnetisation structure raises the prospect of potential applications in magnetic memory devices.

Superconductivity-induced change in magnetic anisotropy in epitaxial ferromagnet-superconductor hybrids with spin-orbit interaction

“…Interestingly, for non-collinear alignment of the F layer moments in spin-valves [10][11][12] or Josephson junctions [13][14][15][16][17][18][19][20][21][22], an enhancement in the proximity effect is found due to the generation of long-range triplet Cooper pairs, immune to the pair-breaking exchange field in the F layers. So far, the reciprocal modification of the static properties of the ferromagnet by superconductivity has been limited to restructuring [23] and pinning of magnetic domains walls (DWs) by Meissner screening and vortexmediated pinning of DWs [24][25][26][27].…”

“…Indeed, our experiments show that magnetization, when locked below T C in the (π + π/4) angle, hardly depends on the absolute value of the external field along [110] varied between 0 and 100 Oe. Moreover, simulations of the vortex-DW interaction using MuMax3 [52] and TDGL codes [59] discard the vortex mediated DW pinning [26,27] scenario including when interfacial magnetic defects created by misfit dislocations [54] are considered (see Supplemental material S6 [49]). The vortex pinning mechanism also contradicts that only the (0 − π) field rotation span (Figure 2a) gets affected below T C /2.…”

Electrically Tunable Multiterminal SQUID-on-Tip

“…These include magnetic force microscopy (MFM) 1,2 , magnetic resonance force microscopy (MRFM) [3][4][5] , nitrogen vacancy (NV) centers sensors [6][7][8][9] , scanning Hall probe microscopy (SHPM) [10][11][12] , x-ray magnetic microscopy (XRM) 13 , and micro-or nano-superconducting quantum interference device (SQUID) [14][15][16][17][18][19][20] based scanning microscopy (SSM) [21][22][23][24][25][26][27][28][29][30][31][32] . Scanning micro-and nanoscale SQUIDs are of particular interest for magnetic imaging due to their high sensitivity and large bandwidth 15,19 .…”

“…In recent years, there has been a growing effort to develop and apply nanoscale magnetic imaging tools to address the rapidly evolving fields of nanomagnetism and spintronics. These include magnetic force microscopy (MFM), , magnetic resonance force microscopy (MRFM), − nitrogen vacancy (NV) center sensors, − scanning Hall probe microscopy (SHPM), − X-ray magnetic microscopy (XRM), and micro- or nanosuperconducting quantum interference device (SQUID)-based − scanning microscopy (SSM). − Scanning micro- and nanoscale SQUIDs are of particular interest for magnetic imaging due to their high sensitivity and large bandwidth. , The two main technological approaches to the fabrication of scanning SQUIDs are based on planar lithographic methods ,,− and on self-aligned SQUID-on-tip (SOT) deposition. ,, …”

Internal flux dynamics and stray field-mediated coupling in the AC susceptibility response of Nb/Ni thin-film bilayers

“…It is important to stress that the increment in internal field that is measured has to be carried in and out by vortices, which align preferentially to the applied field. Therefore, a modification of the effective vortex mobility in S via magnetic coupling can be proposed as the mechanism through which perpendicular stray fields in F influence vortex dynamics [8,36,37]. Recent observations of enhanced flux entry produced by a superposition of perpendicular magnetic fields in Nb thin films support this hypothesis [38].…”