Room temperature domain wall pinning in bent ferromagnetic nanowires

We investigate the influence of the domain wall ferromagnetic resonance frequency on the spin transfer torque in a ferromagnetic nanowire. By employing micromagnetic simulations with the spin transfer torque, we find that the domain wall resonance frequency decreases with increasing spin polarized current density, when there is no change in the resonance frequency of the domain itself. Surprisingly, the variation of the resonance frequency is remarkable (> 1.6 GHz) with the s...

We measured the low frequency (10mHz < f < 10Hz) resistance fluctuations (Noise) in single crystalline ferromagnetic Ni nanowires (diameter ~35nm) in the temperature range 80K-300K. The noise spectral power shows 1/f dependence. The nanowires in an applied magnetic field show negative magetoresistance that saturates for H <= HC. The noise spectral power shows a reduction in low applied field and becomes field independent for H >= HC. This indicates that a part of the observed...

We study field-induced domain wall motion in permalloy nanowires with vertically etched nanotrench pinning site. Micromagnetic simulations and electrical measurements are employed to characterize the pinning potential at the nanotrench. It is found that the potential profile for a transverse wall significantly differs from that of a vortex wall, and there is a correlation between the pinning strength and the potential profile. Reliable domain wall pinning and depinning is exp...

The pinning effect of the periodic diameter modulations on the domain wall propagation in FeCoCu individual nanowires is determined by Magnetic Force Microscopy, MFM. A main bistable magnetic configuration is firstly concluded from MFM images characterized by the spin reversal between two nearly single domain states with opposite axial magnetization. Complementary micromagnetic simulations confirm a vortex mediated magnetization reversal process. A refined MFM imaging procedu...

The dynamics of current-induced motion of a magnetic domain wall in a quasi-one-dimensional ferromagnet with both easy-axis and easy-plane anisotropy, is studied. We pay a special attention to the case of a sharp domain wall, and calculate the spin torque created by the electric current. The torque has two components, one of which is acting as a driving force for the motion of the domain wall while the other distorts its shape, forcing thus the magnetic moments to deviate fro...

We study, both analytically and numerically, a spinmotive force arising from inherent magnetic energy of a domain wall in a wedged ferromagnetic nanowire. In a spatially-nonuniform nanowire, domain walls are subjected to an effective magnetic field, resulting in spontaneous motion of the walls. The spinmotive force mechanism converts the ferromagnetic exchange and demagnetizing energy of the nanowire into the electrical energy of the conduction electrons through the domain wa...

Topology is a powerful tool for categorizing magnetization textures, highlighting specific features in both 2D systems, such as thin films or curved surfaces, and in 3D bulk systems. In the emerging field of 3D nanomagnetism within confined geometries, the contributions from both volume and surface must be considered, requiring appropriate topological analysis to obtain a complete view of the system. Here, we consider domain walls in cylindrical magnetic nanowires to illustra...

We have designed a system to study microwave assisted domain wall nucleation in permalloy nanowires. We find a substantial decrease in the nucleation field when microwave fields are applied, in comparison to pulse fields. A clear resonance peak is observed in the frequency dependence of the nucleation field, which coincides with the uniform mode ferromagnetic resonance frequency. Owing to the well-defined nucleation process, the switching field distribution is small in contra...

We demonstrate movement of a head-to-head domain wall through a magnetic nanowire simply by passing an electrical current through the domain wall and without any external magnetic field applied. The effect depends on the sense and magnitude of the electrical current and allows direct propagation of domain walls through complex nanowire shapes, contrary to the case of magnetic field induced propagation. The efficiency of this mechanism has been evaluated and the effective forc...

We consider the dynamics of polarization of a single domain wall in a magnetic nanowire, which is strongly pinned by impurities. In this case the equation of motion for the polarization parameter does not include any other dynamical variables and is nonlinear due to magnetic anisotropy. We calculated numerically the magnetization dynamics for different choices of parameters under short current pulses inducing polarization switching. Our results show that the switching is most...