SPIN

We fabricated Permalloy (Fe₁₉Ni₈₁) nanomembranes rolled-up into compact three-dimensional architectures and experimentally investigated their magnetic and magneto-electric responses. When a magnetic nanomembrane is rolled-up, an additional magnetostatic interaction between the multiple windings emerges. Such kind of magnetostatic interaction, unique to the rolled-up magnetic nanomembranes and not accessible in any other magnetic architecture, is addressed for the first time in this study. An important feature of rolled-up tubes with multiple windings is that the inner and outer windings are formed by a single magnetic sheet; the spin configuration therefore must be continuous. The magnetostatic interaction induces anti-parallel alignment of the spins within adjacent layers of a rolled-up nanomembrane. The interplay between the magnetostatic interaction due to geometrical transformation and the exchange coupling in the film results in a stabilization of stripe domain patterns.

We derive the effective dimensionally reduced Schrödinger equation with spin–orbit interaction (SOI) in low-dimensional electronic strain-driven nanostructures. By employing a method of adiabatic separation among fast normal quantum degrees of freedom and slow tangential quantum degrees of freedom, we show the emergence of a strain-induced Rashba-like SOI. By applying this analysis to one-dimensional (1D) curved quantum wires we demonstrate that the curvature-induced Rashba SOI leads to enhanced spin–orbit effects.

The ground state of hemispherical permalloy magnetic shell is studied. There exist two magnetic phases: the onion state and the vortex one. The phase diagram is systematically analyzed in a wide range of geometrical parameters. Possible transitions between different phases are analyzed using the combination of analytical calculations and micromagnetic simulations.

The dynamics of vortex domain walls (VDWs) in ferromagnetic nanotubes induced with dc and ac magnetic fields is investigated theoretically. Such domain walls (DWs) are physical objects living in a fairly rich energy landscape with paths that can be tailored. In this way, two different Walker fields has been already predicted to appear in the tubes, a fact that was attributed to the breaking of left-right symmetry of the walls. The physical origin of such behavior is the interplay between the curvature of the ferromagnetic nanomembrane and the dipole field of the VDW. In this paper it is predicted that the excitation of such domain walls with time-dependent fields may be useful in a variety of situations. First, to avoid the Walker breakdown (and to increase the average velocity) a time-dependent field can be superimposed to a dc field, allowing to control the wall by trapping it in a potential well. This is achieved with a proper combination of dc and ac fields needed to avoid the wall to overcome the energy barriers associated to the Walker breakdown fields, frustrating then the precessional DW motion and increasing the average DW speed. The wall is further pumped with the time-dependent field in a breathing mode, near the top of the energy barrier. This pumping mechanism may be also useful for the generation of spin waves.

Stretchable magneto-resistive sensing elements have been introduced lately as a novel component providing magnetic functionality to stretchable consumer electronics involving smart skin or medical diagnostic applications. While spin valves already revealed high stretchability and reliability, GMR multilayers still lack mechanical compliance and production yield. Here, we report on two crucial improvements in fabrication of GMR multilayers to address these limiting issues. On the one hand, we increase the stretchability of wrinkled magnetic nanomembranes on free-standing elastomer membranes by photolithographically structuring them into a meander pattern. The meander can be regarded as a 2D spring, which can accommodate tensile strains in addition to the apparent wrinkling. On the other hand, we highlight a self-healing effect of GMR multilayers, which occurs due to a thermally induced pre-strain in the elastic support. This causes the soft membrane to contract after the GMR elements are prepared on top and closes cracks often induced during fabrication. Relying on this feature we are able to restore the full GMR performance, even if the magneto-sensitive element initially appeared to be without electrical contact before contraction of the free-standing soft membrane.

This review paper shows some methods to study electrons with spin transport properties. We focus on spin precession patterns with the influence of the spin orbital interaction (SOI) by different way to discuss the spin transport on curved system. This paper can be divided into three parts. The first part is studying the spin precession patterns in the U-shaped 1D wire by introducing a confined potential. In the second part, we introduce a non-Abelian spin–orbital gauge field to study electrons transport on a curved surface. The third part is a generalized form of part one, we study exact Hamiltonians for Rashba and cubic Dresselhaus SOIs on a curved surface. We can see a lot of significant influence of SOI on curved system in this review paper.

We investigate the magnetic field-dependent spin-wave spectrum of a rolled-up permalloy film by means of time-resolved scanning-Kerr-microscopy. We find several quantized spin-wave modes including the ferromagnetic resonance of the structure.

We investigate the effects of piezoelectric-generated strain on the magnetization configuration of Ni nanostructures fabricated on pre-poled piezoelectric (011) [Pb(Mg_0.33Nb_0.66)O₃]_0.68–[PbTiO₃]_0.32 (PMN–PT) by high resolution X-ray microscopy. We observe a strong uniaxial anisotropy in the Ni nanostructures, due to the relaxation of the substrate following the deposition of the Ni. The anisotropy can be modified by the application of an electric field to the piezoelectric substrate (thus generating a piezoelectric strain in the system) through the magneto-elastic effect. By applying an electric field to the PMN–PT, the magnetization configuration in nanostructured Ni squares and rings was reversibly manipulated with a high reproducibility.

Curved geometries like nanotubes and flexible membranes generally differ from flat films by internal strain, geodesic pathways for transport phenomena, and a break of the local inversion symmetry. In ferromagnetism, these characteristics can lead to surprising effects, especially when the curvature radius reaches intrinsic length scales, like the domain wall width or the magnon wave length. Simulation studies demonstrate that curved ferromagnetic thin films display magnetochiral properties similar to the Dzyaloshinskii–Moriya interaction (DMI). In close analogy to the emerging field of flexoelectricity, it is suggested that the controlled bending of ferromagnetic membranes provides a new, reversible and universal method to manipulate their magnetic properties.