DYNAMIC

Energy assisted magnetization reversal - dynamics and thermal effects

 

Financed by the Romanian National Authority for Scientific Research, CNCS – UEFISCDI,
project   PN-II-RU-TE-2012-3-0439,   no. 25 / 2013


Aim

Objectives

Team

Results

Conferences

Objectives


  • O1. Implementation of a set of numerical programs for stochastic magnetization dynamics.


  • Within this first objective we will analyze the dynamic approach to micromagnetics based on
    Langevin dynamics / stochastic Landau-Lifshitz-Gilber (sLLG) equation and on Landau-Lifshitz-Bloch (LLB) equation. These equations will be systematically analyzed and compared, both in terms of dynamics and thermal stability. Because simulation tools efficacy is dependent not only on the accuracy of their calculations but also on the skills of choosing appropriate models and input values, we have to decide which model is more suitable for the implementation of our project.

  • O2. Thermodynamics of the phenomena involved in heat assisted magnetization reversal.


  • To realize energy assisted magnetization reversal (EAMR) technology multiple challenges lie ahead to understand the heating and cooling dynamics, to optimize the process and reduce the power consumption. To obtain high recording density EAMR should occur in a very short period of time, typically nanoseconds or even sub-nanoseconds, i.e., shorter than the time of thermal equilibration in the system. Such a pulse brings the medium into a strongly nonequilibrium state, where a conventional description of magnetic phenomena in terms of classical thermodynamics is no longer valid, and we have to use the nonequilibrium thermodynamics’ tools. Also, during the heating process in the magnetic system appear the thermal stresses which induce magnetoelastic energy, modifying magnetic state of the system, and for some materials and geometry parameters, the values of the thermal stresses are larger than their specific elastic limits. Over this elastic limit the system is plastically deformed and a permanent magnetic anisotropy is induced, modifying the magnetic behavior of the system. Therefore, the thermal stresses become an important parameter in the study of thermal processes in the magnetic materials, which cannot be ignored in applications. During the objective O2 we will analyze different thermal processes produced by sources as laser or electric current applied to the magnetic systems for a finite time. The thermal distribution and thermal stresses generated by the thermal gradients and magnetoelastic energy will be studied for different magnetic systems, for example as a function of the laser/current pulse shape and length.

  • O3. Experimental study of a system of identical particles with controlled interactions. Dependence of magnetization reversal of magnetic field orientation and temperature.


  • During the objective O3 we intend to prepare two-dimensional arrays of magnetic nanostructures. In order to study the size effect and the transitions single domain – pseudosingle domain – multidomain we will prepare a series of samples with different dimensions of the magnetic structures and different distances between them so that the value of magnetostatic interactions remains unchanged. Series of samples with different interactions will be also studied.

  • O4. Study of the behavior of systems of particles under the simultaneous action of dc and ac magnetic fields.


  • Static characterization of our samples will be completed with dynamic characterization using susceptibility and FMR measurements. Similar to the static case, the dependence on magnetic fields orientation and interactions will be analyzed. The simulation tools developed in O1 will be used in order to explain the experimental observations. We will also continue our study regarding the microwave assisted switching.

  • MO. Managerial objective.


  • The coordination of research activities and financial administration issues (salary payment, procurement of equipment and materials, organizing the mobility plan). Elaboration of technical and financial reports, web page of the project, planning the dissemination events and publication in scientific journals.


MODx - Mollio