The soft/hard composite patterned media have potential to be the next generation of magnetic recording, but the composing modes of soft and hard materials have not been investigated systematically. L10 FePt-based soft...The soft/hard composite patterned media have potential to be the next generation of magnetic recording, but the composing modes of soft and hard materials have not been investigated systematically. L10 FePt-based soft/hard composite patterned media with an anisotropic constant distribution are studied by micromagnetic simulation. Square arrays and hexagonal arrays with various pitch sizes are simulated for two composing types： the soft layer that encloses the hard dots and the soft layer that covers the whole surface. It is found that the soft material can reduce the switching fields of bits effectively for all models. Compared with the first type, the second type of models possess low switching fields, narrow switching field distributions, and high gain factors due to the introduction of inter-bit exchange coupling. Furthermore, the readout waveforms of the second type are not deteriorated by the inter-bit soft layers. Since the recording density of hexagonal arrays are higher than that of square arrays with the same center-to-center distances, the readout waveforrns of hexagonal arrays are a little worse, although other simulation results are similar for these two arrays.展开更多
During the process of directional solidification,laser remelting/solidification in the layer on sintered magnets, die-upsetting of cast magnets,or die-upsetting of nano-composites,the arrangements of the easy-magnetiz...During the process of directional solidification,laser remelting/solidification in the layer on sintered magnets, die-upsetting of cast magnets,or die-upsetting of nano-composites,the arrangements of the easy-magnetization-axes of the hard magnetic phases(Nd2Fe14B,SmCo5 or Sm2Co17 type)in their designed directions have been studied.In Fe-Pt nano-composite magnets,attempts have been taken to promote phase transformation from disordered,soft magnetic A1 to ordered,hard magnetic L10 FePt phase at reduced temperatures.The dependence of the magnetization and reversal magnetization processes on the microstructures,involving the morphology and three critical sizes of particles of the FePt nano-composite magnets,are summarized. With the decrease of the nominal thickness of the anisotropic FePt film epitaxially grown on the single crystal MgO(001)substrate, the reversal magnetization process firstly changes from full domain wall displacement to partial magnetic wall pinning related to the morphology change,where the coercive force increases abruptly.The reversal magnetization process secondly changes from magnetic wall pinning to incoherent magnetization rotation associated with the particles being below the first critical size at which multi-domain particles turn into single domain ones,where the coercive force is still increased.And the reversal magnetization mode thirdly changes from incoherent to coherent rotation referred to the second critical size,where the increase of the coercive force keeps on.However,when the particle size decreases to approach the third critical size where the particles turn into the supperparamagnetic state,the coercive force begins to decrease due to the interplay of the size effect and the incomplete ordering induced by the size effect.Meanwhile,due to the size effect,Curie temperature of the ultra-small FePt particles reduces.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51171086 and 61272076)the Young Scientists Fund of the National Natural Science Foundation of China(Grant No.61003041)
文摘The soft/hard composite patterned media have potential to be the next generation of magnetic recording, but the composing modes of soft and hard materials have not been investigated systematically. L10 FePt-based soft/hard composite patterned media with an anisotropic constant distribution are studied by micromagnetic simulation. Square arrays and hexagonal arrays with various pitch sizes are simulated for two composing types： the soft layer that encloses the hard dots and the soft layer that covers the whole surface. It is found that the soft material can reduce the switching fields of bits effectively for all models. Compared with the first type, the second type of models possess low switching fields, narrow switching field distributions, and high gain factors due to the introduction of inter-bit exchange coupling. Furthermore, the readout waveforms of the second type are not deteriorated by the inter-bit soft layers. Since the recording density of hexagonal arrays are higher than that of square arrays with the same center-to-center distances, the readout waveforrns of hexagonal arrays are a little worse, although other simulation results are similar for these two arrays.
基金Project(2004CCA04000)supported by the National Basic Research Program of ChinaProject(50744014)supported by the National Natural Science Foundation of China+3 种基金Project(2008C21046)supported by Science and Technology Department of Zhejiang Province,ChinaProject(Y406389)supported by Zhejiang Provincial Natural Science Foundation of ChinaProject(2006B100054)supported by Ningbo Bureau of Science and Technology,ChinaProject supported by K.C.Wong Magna Found in Ningbo University,China
文摘During the process of directional solidification,laser remelting/solidification in the layer on sintered magnets, die-upsetting of cast magnets,or die-upsetting of nano-composites,the arrangements of the easy-magnetization-axes of the hard magnetic phases(Nd2Fe14B,SmCo5 or Sm2Co17 type)in their designed directions have been studied.In Fe-Pt nano-composite magnets,attempts have been taken to promote phase transformation from disordered,soft magnetic A1 to ordered,hard magnetic L10 FePt phase at reduced temperatures.The dependence of the magnetization and reversal magnetization processes on the microstructures,involving the morphology and three critical sizes of particles of the FePt nano-composite magnets,are summarized. With the decrease of the nominal thickness of the anisotropic FePt film epitaxially grown on the single crystal MgO(001)substrate, the reversal magnetization process firstly changes from full domain wall displacement to partial magnetic wall pinning related to the morphology change,where the coercive force increases abruptly.The reversal magnetization process secondly changes from magnetic wall pinning to incoherent magnetization rotation associated with the particles being below the first critical size at which multi-domain particles turn into single domain ones,where the coercive force is still increased.And the reversal magnetization mode thirdly changes from incoherent to coherent rotation referred to the second critical size,where the increase of the coercive force keeps on.However,when the particle size decreases to approach the third critical size where the particles turn into the supperparamagnetic state,the coercive force begins to decrease due to the interplay of the size effect and the incomplete ordering induced by the size effect.Meanwhile,due to the size effect,Curie temperature of the ultra-small FePt particles reduces.
