Ferromagnetism Properties And Its Mechanism Research Of SiC And BN Nanomaterials

Diluted magnetic semiconductors(DMSs),with excellent semiconductive and ferromagnetic properties,own the charge and spin properties of electrons,which have been used in a wide range of applications in future spin electronic devices.Therefore,there is an urgent need to develop new diluted magnetic semiconductor materials and explore the origin of ferromagnetism.In this thesis,we have mainly researched high temperature ferromagnetic mechanism of DMSs in low dimensions,in order to explore the origin of magnetic moments.On the one hand,high temperature ferromagnetism is found in zero-dimensional SiC nanoparticles and two-dimensional BN nanoplates,and the structure,shape,optics and magnetic properties of these materials are systematically studied.On the other hand,by regulating the surface defects of materials and combining with the first principle calculation,the mechanism of the stable high-temperature ferromagnetism of DMSs at low dimensional scale is revealed,which provides the theoretical and experimental basis for its application in spintronic devices.The main research contents and results of this thesis are as follows:1.Pure phase zero dimensional SiC nanoparticles were successfully synthesized by high energy ball milling method.The structure,morphology and magnetic properties were systematic researched.Magnetic measurement at room temperature indicate that all milled samples show typical room temperature ferromagnetic(RT FM),while the bulk SiC material present diamagnetism.The saturation magnetization(MS)increases monotonically from 0.0006 emu/g to 0.0032 emu/g,with increasing of milling time.Besides,the high temperature magnetic measurements indicate that SiC nanoparticles show high temperature ferromagnetism and still exhibit hysteresis phenomenon at 800 K(Ms:0.0015 emu/g).The results of XRD,Raman,ESR and PL manifest that the high ferromagnetism of SiC nanoparticles are related to surface defects.2.Two-dimensional BN nanoplates were synthesized via high-energy ball milling method.Magnetic measurements at room temperature indicate that BN nanoplates exhibit distinct RT FM.The Ms increases monotonically from 0.015 to 0.032 emu/g with increasing of milling time,while the bulk BN powders present diamagnetism.Besides,the high temperature magnetic measurements indicated that the Tc of the BN nanoplates is greater than 900 K.Combining with results of Raman,ESR,XPS and the first principle calculation found that the high ferromagnetism of BN nanoplates are related to surface nitrogen defects.