The collective dynamics of magnetic domain wall under electric current is studied in the form of spin transfer torque(STT). The out-of-plane STT induced effective force is obtained based on the Landau-Lifshitz-Gilbert...The collective dynamics of magnetic domain wall under electric current is studied in the form of spin transfer torque(STT). The out-of-plane STT induced effective force is obtained based on the Landau-Lifshitz-Gilbert(LLG) equation including microscopic STT terms. The relation between microscopic calculations and collective description of the domain wall motion is established. With our numerical calculations based on tight binding free electron model, we find that the non adiabatic out-of-plane torque components have considerable non-local properties. It turns out that the calculated effective forces decay significantly with increasing domain wall widths.展开更多
The influence of particle size and morphology on grain refinement in low stacking fault energy(SFE)alloys was studied by comparing the grain structures in single-and multi-phase Al-bronze(AB)alloys following equal cha...The influence of particle size and morphology on grain refinement in low stacking fault energy(SFE)alloys was studied by comparing the grain structures in single-and multi-phase Al-bronze(AB)alloys following equal channel angular pressing(ECAP)between 350 and 500℃.In particular,nickel aluminium bronze(NAB)was chosen as it contained both coarse and fine rounded particles,as well as a lamellar phase which evolved during ECAP.Grain refinement in the single-phase alloy was achieved through dynamic recrystallisation initiated at deformed twin boundaries.By contrast,different mechanisms were observed in the particle-containing NAB.Recrystallisation around the coarseκⅡparticles(~5μm)was promoted through particle stimulated nucleation(PSN),whereas recrystallisation in the region of the fineκⅣ(~0.4μm)was delayed due to the activation of secondary slip.Grain refinement in areas of the lamellarκⅢshowed significant variation,depending on the lamellar orientation relative to the shear plane of ECAP.As the lamellae deformed,numerous high angle grain boundaries were generated between fragments and served as nucleation sites for recrystallisation,while PSN occurred around spheroidised lamellae.The spreading of theκⅢparticles by ECAP then enhanced the total area of recrystallised grains.展开更多
基金supported by NSF of China(Grant No.60825405)MOST of China(2006CB933000)
文摘The collective dynamics of magnetic domain wall under electric current is studied in the form of spin transfer torque(STT). The out-of-plane STT induced effective force is obtained based on the Landau-Lifshitz-Gilbert(LLG) equation including microscopic STT terms. The relation between microscopic calculations and collective description of the domain wall motion is established. With our numerical calculations based on tight binding free electron model, we find that the non adiabatic out-of-plane torque components have considerable non-local properties. It turns out that the calculated effective forces decay significantly with increasing domain wall widths.
文摘The influence of particle size and morphology on grain refinement in low stacking fault energy(SFE)alloys was studied by comparing the grain structures in single-and multi-phase Al-bronze(AB)alloys following equal channel angular pressing(ECAP)between 350 and 500℃.In particular,nickel aluminium bronze(NAB)was chosen as it contained both coarse and fine rounded particles,as well as a lamellar phase which evolved during ECAP.Grain refinement in the single-phase alloy was achieved through dynamic recrystallisation initiated at deformed twin boundaries.By contrast,different mechanisms were observed in the particle-containing NAB.Recrystallisation around the coarseκⅡparticles(~5μm)was promoted through particle stimulated nucleation(PSN),whereas recrystallisation in the region of the fineκⅣ(~0.4μm)was delayed due to the activation of secondary slip.Grain refinement in areas of the lamellarκⅢshowed significant variation,depending on the lamellar orientation relative to the shear plane of ECAP.As the lamellae deformed,numerous high angle grain boundaries were generated between fragments and served as nucleation sites for recrystallisation,while PSN occurred around spheroidised lamellae.The spreading of theκⅢparticles by ECAP then enhanced the total area of recrystallised grains.
