Micromagnetic modeling of the heat-assisted switching process in high anisotropy FePt granular thin films

Abstract

The dynamic process of assisted magnetic switchins has been simulated to investigate the associated physics. The model uses a Voronoi construction to determine the physical structure of the nano granular thin film recording media; and the Landau-Lifshitz-Bloch (LLB) equation is solved to evolve the magnetic system in time. The reduction of the magnetization is determined over a range of peak system temperatures and for a number of anisotropy values. The results show that the HAMR process is not simply magnetization reversal over a thermally reduced energy barrier. To achieve full magnetization reversal (for all anisotropies investigated) an applied field strength of at least 6kOe is required and the peak system temperature must reach at least the Curie point (T c ). When heated to T c the magnetization associated with each grain is destroyed, which invokes the non-precessional linear reversal mode. Reversing the magnetization through this linear reversal mode is favourable, as the reversal time is two orders of magnitude smaller than that associated with precession. Under these conditions, as the temperature decreases to ambient, the magnetization recovers in the direction of the applied field, completing the reversal process. Also the model produces results which are consistent with the concept of thermal writability; when heating the media to T c , the smaller grains require a larger field strength to reverse the magnetization.

Controlled Magnetic Isolation and Decoupling of Perpendicular FePt Films by Capping Ultrathin Cu(002) Nano-Islands

“…The ferromagnetic, ordered phase usually showed a high exchange-coupled interaction between the neighboring grains due to the large-grain growth during the thermal process. Thus, the nanocomposite and nanogranular ferromagnetic film structures fabricated at low-temperature conditions have attracted significant attention because of the decoupling of the intergranular interaction that could enhance the signal-to-noise ratio; therefore, they are considered more favorable for the next generation magnetic storage media [13][14][15][16][17][18][19][20][21][22][23]. Many attempts have been made to propose the effect of top or under layers; the additive effect of metal oxides and nitride elements is a successful method to control the chemical ordering, microstructure, magnetic coupling, and crystalline orientation of the L1 0 magnetic thin films to meet the requirements of industrial manufacture, especially in technologically important perpendicular magnetic materials for multifunctional device applications [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42].…”