| Since the Internet technology was born,the magnetic recording technology had started to move forward the revival road of prosperity and development.More and more researchers were devoted to the investigation and development of magnetic recording materials.It is for this reason that the magnetic recording technology provides a solid foundation for the rapid and stable development of the Internet today.Nowadays,our mankind has already entered the Internet era and is moving toward the age of big data.Data security and accessibility issues will soon be highlighted in all areas in the big-data age,and the fundamental way to solve these problems is to answer the question: where do we record our data? Therefore,there is an urgent need in the field of magnetic storage to use the new magnetic recording technology to meet the needs of big-data age.As an improved method of traditional magnetic recording technology,heat-assisted magnetic recording technology has received close attention of researchers in the field of magnetic storage.However,there are still many problems that need to be solved in the real application of the magnetic recording industry.Therefore,the major companies have not been introduced yet available products.Compared with thermally assisted magnetic recording technology,however,the advantage of all-optical magnetic switching technology is removing the external write magnetic field constraints directly,which enables the pure all-optical write process.As a new magnetic recording technology,all-optical magnetic switching has unique advantages in many aspects,but there are still a large number of problems that researchers need to work together to resolve.The first problem of developing all-optical magnetic recording technology is obviously the choice of recording media.FePt magnetic material is very eye-catching in magnetic recording field.Researchers consider it as a storage medium for thermally assisted magnetic recording technology in the early time,and therefore accumulated a large number of FePt materials related research results.In recent years,researchers have successfully observed the phenomenon of all-optical magnetic switching on a variety of materials,including the FePt magnetic material.Based on the above reasons,it is of long-term practical significance to deeply study the phenomenon of all-optical magnetic switching observed on FePt material.The basis for an in-depth study of FePt magnetic materials is to establish a usable atomic scale simulation model.Based on the general simulation model,this paper establishes a FePt material simulation model suitable for the research of all-optical magnetic switching.Moreover,through continuous improvement,the whole research process introduced several factors that affect the magnetic characteristics of FePt material to the simulation model.Finally,an enhanced atomic simulation model of L10-FePtAg material was formed.These factors include the superparamagnetic effect caused by the change of the size of the material and the significant enhancement of the L10 phase of the FePt material after Ag doping.With the help of these simulation models,the Curie temperature of FePt materials with different sizes was calculated and the critical dimension of the Curie temperature divergence of FePt material was obtained.Considering that the Curie temperature has an important influence on the magnetic writing process,this paper also established the formula of volume-independent Curie temperature in the small size range which can be applied to make a reasonable estimate of the magnetic writing temperature.In addition,the study of the smallest thermally stable size of FePt material can help researchers effectively predict the highest storage densities for FePt material.Using the simulation model,the thermal stability of FePt materials with different sizes was researched in this paper.The results show that the pure FePt magnetic particle with the size of 8 nm reach the limit of stable information storage.Through the study of thermal stability factor of FePt material,some methods about how to improve uniaxial anisotropy of FePt material are also obtained,which can help us to further reduce the size of the recording particles.In the process of establishing the model of the interaction between laser pulse and FePt material,two effects of laser pulse on the material are considered in this paper: thermal effect and switching field effect,and their respective calculating simulation models are established according to these two effects.Combining the laser-material interaction model with the previously established FePt material model,a simulation system has been developed for the study of all-optical magnetic switching process.Using the simulation system,the paper studies the ultrafast all-opticall magnetic switching of 6 nm L10-FePtAg magnetic particles,and obtains three key stages of magnetization evolution and pulse power upper and lower limits of all-optical switching.To conclude,this paper has conducted an in-depth and comprehensive study on the magnetic recording properties of FePt magnetic materials,which will provide a wealth of valuable data for the preparation and experimental measurement of subsequent FePt materials.Simultaneously,the atomic scale simulation model based on L10-FePtAg magnetic particles established in this paper will also be an advantageous tool for researchers to study the phenomenon of all-optical magnetic switching. |
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