The Micromagnetic Study Of The Recording Media For Energy Assisted Magnetic Recording

Data storage technology develops as one of the most important computer technology,and the recording density boom similar as the Moore’s law.Now the density has arrived at 1Tb/in2 and the magnetic recording technology has already meet the writable limit of the magnetic media.In the beginning of the hard disk magnetic recording,there were several hundred grains in a single bit,now a bit contains less than ten grains.The grain pitch of the media also has been reduced.Therefore the polycrystalline structure,including crystal grains and the disorder grain boundary parameters become important in micromagnetic simulations.One of my major work is introducing the Voronoi tessellation into the micromagnet-ics.Comparing with the grain seed random growth method formerly used in our group,the grain structure generated by the Voronoi tessellation is closer to the polycrystalline recording media.The Co/Pt film is studied by using the conventional micromagnetic method and the hysteresis loops of varies parameters are simulated.This study found the optimal parameter set of the media and point out the direction for the high density Co/Pt film preparation.The results indicate that the parameters of the grain boundary will influence the slope and squareness of the hysteresis loop,which are important for recording.These parameters can be adjusted by doping certain elements properly.Later recording simulation works in our group are based on the Voronoi tessellation.To further push the storage density limit forward to satisfy the increasing demand of information storage,the microwave assisted magnetic recording(MAMR)and the heat assisted magnetic recording(HAMR)technology are proposed.These design schemes add the microwave or laser generator to assist the writing process.I studied these two designs by micromagnetic methods.Based on the Voronoi tessellation grain structure,I used the hybrid Monte Carlo(HMC)method developed by our group to simulate the magnetic properties of the materials at finite temperature.The L10-FePt hard magnetic film and the FeCo soft magnetic film are simulated by this method.The L10-FePt film is a promising media for HAMR.In the simulation,the material parameters,the distribution of the anisotropy axis,the substrate and the thermal effect are studied.The FeCo soft magnetic film has the largest saturation magnetization and large spin polarization,which is suitable for the write head and is a significant film in spintronics.In the simulation,the anisotropy,the normal and shear stress and the thermal effect are studied.I also studied the microwave assisted magnetic recording based on an ECC double particle model.The flip features under the microwave of varies frequency and polarization model are simulated and we found the optimal frequency for this certain parameter set of the media.I also found when the model applied the microwave of two certain frequencies,the particles will flip without external field.I also explained this phenomenon theoretically.