Search results for "Magnetization dynamics"
showing 10 items of 35 documents
An antidamping spin–orbit torque originating from the Berry curvature
2014
Magnetization switching at the interface between ferromagnetic and paramagnetic metals, controlled by current-induced torques, could be exploited in magnetic memory technologies. Compelling questions arise regarding the role played in the switching by the spin Hall effect in the paramagnet and by the spin-orbit torque originating from the broken inversion symmetry at the interface. Of particular importance are the antidamping components of these current-induced torques acting against the equilibrium-restoring Gilbert damping of the magnetization dynamics. Here, we report the observation of an antidamping spin-orbit torque that stems from the Berry curvature, in analogy to the origin of the …
Role of spin diffusion in current-induced domain wall motion for disordered ferromagnets
2015
Current-induced spin transfer torque and magnetization dynamics in the presence of spin diffusion in disordered magnetic textures is studied theoretically. We demonstrate using tight-binding calculations that weak, spinconserving impurity scattering dramatically enhances the nonadiabaticity. To further explore this mechanism, a phenomenological drift-diffusion model for incoherent spin transport is investigated. We show that incoherent spin diffusion indeed produces an additional spatially dependent torque of the form ∼∇ 2 [m × (u · ∇)m] + ξ ∇ 2 [(u · ∇)m], where m is the local magnetization direction, u is the direction of injected current, and ξ is a parameter characterizing the spin dyna…
Spinmotive force due to motion of magnetic bubble arrays driven by magnetic field gradient
2014
Interaction between local magnetization and conduction electrons is responsible for a variety of phenomena in magnetic materials. It has been recently shown that spin current and associated electric voltage can be induced by magnetization that depends on both time and space. This effect, called spinmotive force, provides for a powerful tool for exploring the dynamics and the nature of magnetic textures, as well as a new source for electromotive force. Here we theoretically demonstrate the generation of electric voltages in magnetic bubble array systems subjected to a magnetic field gradient. It is shown by deriving expressions for the electric voltages that the present system offers a direc…
Accessing fast magnetization dynamics by XPEEM: Status and perspectives
2006
Abstract Being already well established as a versatile technique for high-resolution static magnetic domain imaging, X-ray photoemission electron microscopy (XPEEM) is now also capturing the field of time-resolved magnetic investigations. Using appropriate operation modes at synchrotron radiation sources, a time resolution of 10 ps and less can be achieved in recent magnetodynamics studies, giving access even to phenomena involving precessional processes.
Electrically Controlled Pumping of Spin Currents in Topological Insulators
2011
Pure spin currents are shown to be generated by an electrically controlled quantum pump applied at the edges of a topological insulator. The electric rather than the more conventional magnetic control offers several advantages and avoids, in particular, the necessity of delicate control of magnetization dynamics over tiny regions. The pump is implemented by pinching the sample at two quantum point contacts and phase modulating two external gate voltages between them. The spin current is generated for the full range of parameters. On the other hand, pumping via amplitude modulation of the inter-boundary couplings generates both charge and spin currents, with a pure charge current appearing o…
Butterfly hysteresis curves generated by adiabatic Landau-Zener transitions
2006
Butterfly hysteresis curves observed in dynamical magnetization measurements on systems of low-spin magnetic molecules such as ${\mathrm{V}}_{15}$ can be explained by the interplay of adiabatic Landau-Zener transitions and relaxation. We investigate the magnetization dynamics analytically in the basis of the adiabatic energy levels of the spin $1∕2$, to a qualitative accordance with experimental observations. In particular, reversible behavior is found near zero field, the corresponding susceptibility being bounded by the equilibrium and adiabatic susceptibilities.
Magnetization changes visualized using photoemission electron microscopy
2004
Abstract Photoemission electron microscopy was used to visualize the motion of magnetic domains on a sub-nanosecond timescale. The technique exploits the imaging of magnetic domains using soft X-ray circular dichroism, with the special feature that the instrument utilizes a fast image acquisition system with intrinsic 125 ps time resolution. The overall time resolution used is about 500 ps. Different domains and domain movements have been observed in lithographically-produced Permalloy structures on a copper microstrip-line. A current pulse of I=0.5 A with rise times of about 300 ps switched the Permalloy islands from a Landau-Lifshitz type domain configuration into metastable s-state domai…
Transient spatio-temporal domain patterns in permalloy microstructures induced by fast magnetic field pulses
2006
The response of multidomain flux-closure structures (Landau states) in micrometer-scale magnetic thin-film elements upon fast magnetic field pulses leads to the excitation of magnetic eigenmodes and to short-lived domain patterns that do not occur in quasi-static remagnetisation. Such transient spatio-temporal patterns and particular detail features are discussed. Examples are presented for permalloy platelets of various shapes and sizes. Dynamic series of domain patterns with variable delay between field pulse and photon pulse (synchrotron radiation) have been taken using stroboscopic XMCD-PEEM. Precessional remagnetisation starts at the domain boundaries. The damped precessional motion pr…
Stroboscopic XMCD-PEEM Imaging
2007
Abstract This article summarizes recent results on magnetization dynamics obtained with time-resolved photoemission electron microscopy (PEEM) using X-ray magnetic circular dichroism as contrast mechanism. Time resolution is performed by a stroboscopic technique that is exclusively sensitive to reversible processes, but offers a very high time resolution only limited by the X-ray pulse width. A time resolution of 20 ps in combination with a lateral resolution of 100 nm has been achieved.
Giant enhancement to spin battery effect in superconductor/ferromagnetic insulator systems
2021
We develop a theory of the spin battery effect in superconductor/ferromagnetic insulator (SC/FI) systems taking into account the magnetic proximity effect. We demonstrate that the spin-energy mixing enabled by the superconductivity leads to the enhancement of spin accumulation by several orders of magnitude relative to the normal state. This finding can explain the recently observed giant inverse spin Hall effect generated by thermal magnons in the SC/FI system. We suggest a nonlocal electrical detection scheme which can directly probe the spin accumulation driven by the magnetization dynamics. We predict a giant Seebeck effect converting the magnon temperature bias into the nonlocal voltag…