Analysis Of Magnetization Dynamics Research Articles

Effect of antiphase boundaries on the magnetic properties of La2CoMnO6

We present a comparative study of structural and magnetic properties of the as-grown and annealed samples of double perovskite, La2CoMnO6. The single monoclinic (P21/n) phase has been achieved for both the samples. Electron microscopy highlights the change in morphology of the as-grown and annealed samples, with the annealed sample having more grain boundaries and bigger particle sizes. The annealing in presence of oxygen leads to increase in the population of antiphase boundaries, which is supported by the decreases in the remanent and saturation magnetizations. An analysis of magnetization dynamics by means of AC susceptibility shows four different magnetic transitions, with two high temperature ferromagnetic transitions and two cluster glass-like states emerging at low temperatures, which appear almost identical in both the as-grown and annealed samples.

Nonstationary magnetization dynamics driven by spin transfer torque

This paper shows that the presence of two dynamical regimes, characterized by different precessional axes, is the origin of the nonmonotonic behavior of the output integrated power for large-amplitude magnetization precession driven by spin-polarized current in nanoscale exchange-biased spin valves. In particular, an abrupt loss in the integrated output power exists at the transition current between those two regimes. After the introduction of a time-frequency analysis of magnetization dynamics based on the wavelet transform, we performed a numerical experiment by means of micromagnetic simulations. Our results predicted that, together with a modulation of the frequency of the main excited mode of the magnetization precession, at high nonlinear dynamical regime the instantaneous output power of the spin-torque oscillator can disappear and then reappear at nanosecond scale.

Numerical study on microwave-assisted magnetization reversal of magnetic particles several tens of nanometers wide with perpendicular anisotropy

Microwave-assisted magnetization reversal (MAMR) is numerically investigated for perpendicularly magnetized particles with a natural ferromagnetic resonance frequency of 22.5 GHz. The precession angle of magnetization can be enhanced intensively by increasing the amplitude of the ac hard-axis field with an optimum frequency. However, the precession of magnetization about the easy axis becomes unstable as the precession angle reaches a critical value because the easy-axis component of the effective field exerted on the magnetization becomes zero. The analysis of magnetization dynamics in MAMR showed that the precession of magnetization about an in-plane axis, appearing after the easy-axis component of the effective field becomes zero, plays an important role in the irreversible switching of magnetization.

Bifurcation analysis of magnetization dynamics driven by spin transfer

Nonlinear magnetization dynamics under spin-polarized currents is discussed by the methods of the theory of nonlinear dynamical systems. The fixed points of the dynamics are calculated. It is shown that there may exist 2, 4, or 6 fixed points depending on the values of the external field and of the spin-polarized current. The stability of the fixed points is analyzed and the conditions for the occurrence of saddle-node and Hopf bifurcations are determined.