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Magnetic materials host a wealth of nonlinear dynamics, textures, and topological defects. This is possible due to the competition between strong nonlinearity and dispersion that act at the atomic scale as well as long-range interactions. However, these features are difficult to analytically and numerically study because of the vastly different temporal and spatial scales involved. Here, we present a pseudo-spectral approach for the Landau-Lifshitz equation that invokes energy and momentum conservation embodied in the magnon dispersion relation to accurately describe both atomic and continuum limits. Furthermore, this approach enables analytical study at every scale. We show the applicability of this model in both the continuum and atomic limit by investigating modulational instability and ultrafast evolution of magnetization due to transient grating, respectively, in a 1D ferromagnetic chain with perpendicular magnetic anisotropy. This model provides the possibility of grid-independent multiscale numerical approaches that will enable the description of singularities within a single framework.

In this work, we propose helicity-dependent switching (HDS) of magnetization of Co/Pt for energy efficient optical receiver. Designing a low power optical receiver for optical-to-electrical signal conversion has proven to be very challenging. Current day receivers use a photodiode that produces a photocurrent in response to input optical signals, and power hungry trans-impedance amplifiers are required to amplify the small photocurrents. Here, we propose light helicity induced switching of magnetization to overcome the requirement of photodiodes and subsequent trans-impedance amplification by sensing the change in magnetization with a magnetic tunnel junction (MTJ). Magnetization switching of a thin ferromagnet layer using circularly polarized laser pulses have recently been demonstrated which shows one-to-one correspondence between light helicity and the magnetization state. We propose to utilize this phenomena by using digital input dependent circularly polarized laser pulses to directly switch the magnetization state of a thin Co/Pt ferromagnet layer at the receiver. The Co/Pt layer is used as the free layer of an MTJ, the resistance of which is modified by the laser pulses. With the one-to-one dependence between input data and output magnetization state, the MTJ resistance is directly converted to digital output signal. Our device to circuit level simulation results indicate that, HDS based optical receiver consumes only 0.124 pJ/bit energy, which is much lower than existing techniques., Comment: Under review in Physical Review Applied

Using the Landau-Lifshitz-Bloch (LLB) equation for ferromagnetic materials, we derive analytic expressions for temperature dependent absorption spectra as probed by ferromagnetic resonance (FMR). By analysing the resulting expressions, we can predict the variation of the resonance frequency and damping with temperature and coupling to the thermal bath. We base our calculations on the technologically relevant L1$_0$ FePt, parameterised from atomistic spin dynamics simulations, with the Hamiltonian mapped from ab-initio parameters. By constructing a multi-macrospin model based on the LLB equation and exploiting GPU acceleration we extend the study to investigate the effects on the damping and resonance frequency in ${\mu}$m sized structures., Comment: 10 pages, 8 figures