A. Belkin

Guiding superconducting vortices with magnetic domain walls.

We demonstrate a unique prospect for inducing anisotropic vortex pinning and manipulating the directional motion of vortices using the stripe domain patterns of a uniaxial magnetic film in a the superconducting/ferromagnetic hybrid. Our observations can be described by a model, which considers interactions between magnetic charges of vortices and surface magnetic charges of domains resulting in the enhanced pinning of vortices on domain walls.

Adjustable superconducting anisotropy in MoGe-permalloy hybrids.

We studied the magneto-transport properties of magnetically coupled superconducto ferromagnet MoGe/Permalloy bilayers. The rotatable anisotropy Permalloy ferromagnet with stripe domain structure induces in-plane anisotropy in superconducting order parameter. Superconducting phase diagram shows that near the superconductor-normal state phase boundary the superconductivity is localized in narrow mesoscopic channels just above the magnetic domain walls. By changing the in-plane direction of magnetic stripe domains it is possible to re-configure the direction of the superconducting channels and controllably rotate the direction of the in-plane anisotropy axis in the superconductor.

Adjustable Superconducting Anisotropy in Superconductor-Ferromagnet Bilayers

We demonstrate novel magneto-transport properties of magnetically coupled superconductor-ferromagnet (MoGe/Permalloy) bilayers. Ferromagnetic Permalloy film exhibiting stripe domains with rotatable anisotropy induces modulation of the order parameter in the superconducting thin film. Domain-wall superconductivity is localized above the magnetic domain walls forming mesoscopic superfluid channels. We can achieve non-volatile re-configuration of the in-plane direction of the superconducting channels by changing the orientation of the stripe domains in the Permalloy. We discuss the influence of magnetic domain structure on Abrikosov vortex dynamics in this system.

Switching of magnetic domains in Permalloy microstructures using two-dimensional electron gas

The authors demonstrate the ability to monitor and alter the magnetization state of microscopic Permalloy element deposited on the active area of a two-dimensional electron gas (2DEG) Hall probe using the current through the 2DEG. Magnetic force microscopy imaging shows the exact magnetization state of the Permalloy thin film ellipse at different applied magnetic fields. Recorded Hall voltage signal provides information on local magnetization of the ferromagnetic element at the same time. Application of short, but intense current pulses through the Hall probe changes the magnetization state of the Permalloy ellipse.

Dimensionality crossover in vortex dynamics of magnetically coupled F–S–F hybrids

We report on the vortex dynamics in magnetically coupled F-S-F trilayers extracted from the analysis of the resistance-current isotherms. The superconducting thin film that is conventionally in the 2D vortex limit exhibits quite different behavior when sandwiched between ferromagnetic layers. The value of the dynamic critical exponent strongly increases in the F-S-F case due to screening of the stray vortex field by the adjacent ferromagnetic layers, leading to an effective dimensional crossover in vortex dynamics. Furthermore, the directional pinning by the magnetic stripe domains induces anisotropy in the vortex glass transition temperature and causes metastable avalanche behavior at strong driving currents.