Magnetic properties of a two sublattice ferrimagnet with antiferromagnetic exchange interaction inside one of the sublattices are calculated within the framework of the molecular field theory taking into account the a...Magnetic properties of a two sublattice ferrimagnet with antiferromagnetic exchange interaction inside one of the sublattices are calculated within the framework of the molecular field theory taking into account the anisotropy of unstable sublattice. The magnetization curves of single crystal GdMn 2Ge 2 for the magnetic field parallel and perpendicular to the c axis at different temperatures are calculated. Field induced magnetic phase transitions in GdMn 2Ge 2 are discussed. Calculated H T magnetic phase diagrams are in fair agreement with experimental data.展开更多
The crystal and electronic structures of LaNi4.75Sn0.25 intermetallics and LaNi4.5Sn0.5Hy （y=2.0, 2.5） intermediate phase have been investigated by the fullpotential linearized augmented plane wave （FP-LAPW） metho...The crystal and electronic structures of LaNi4.75Sn0.25 intermetallics and LaNi4.5Sn0.5Hy （y=2.0, 2.5） intermediate phase have been investigated by the fullpotential linearized augmented plane wave （FP-LAPW） method. Hydrogen occupation sites in LaNi4.5Sn0.5Hy have been determined based on Westlake＇s criterions： （1） the minimum hole radiuS is 0.04 nm; （2） the minimum H-H distance is 0.21 nm; as well as geometry optimizations and internal coordinates optimizations. We find that hydrogen atoms prefer to occupy the 12n＊, 6m, 12o, 6m＊ sites in LaNi4.5Sn0.5H2.0 and the 6m＊, 4h, 6m, 12o, 12n＊ sites in LaNi4.5Sn0.5H2.5. The specific coordinates of hydrogen atoms in LaNi4.5Sn0.5Hy are also determined. The results show that hydrogen atoms tend to keep away from tin atoms. The maximum hydrogen content decreases compared with LaNi5. The interactions between Sn and Ni with H play a dominate role in the stability of LaNi4.5Sn0.5-H system. Lattice expansion and increment of Fermi energy EF show that both Sn and H atoms decrease structural stability of these alloys.展开更多
The influence of rare earth element Dy on martensitic transformation and magnetic properties of Co-Ni-Al alloy was studied.The results showed that the microstructure of the sample has a dual-phase structure（γ-phase ...The influence of rare earth element Dy on martensitic transformation and magnetic properties of Co-Ni-Al alloy was studied.The results showed that the microstructure of the sample has a dual-phase structure（γ-phase and martensite）.The rare earth element Dy was segregated in Co-richγ-phase and took the place of Co after its addition into the Co-Ni-Al alloy.As Dy content increased to over 0.5at.%,the grain was refined and the rare earth intermetallic compounds Co5 Dy were precipitated inγ-phase.Meanwhile,one-step thermo-elastic martensitic transformation occurred in the sample,wherein the phase transformation temperature significantly increased with rising Dy content.The martensite had a tetragonal L10 structure with a（111）twinning plane.Furthermore,the sample exhibited obvious hysteresis behaviors in the magnetic hysteresis loops.In addition,the saturation magnetization,coercivity,retentivity and magnetocrystalline anisotropy were significantly enhanced owing to the bigger radius of Dy which took the place of Co in the alloy.展开更多
文摘Magnetic properties of a two sublattice ferrimagnet with antiferromagnetic exchange interaction inside one of the sublattices are calculated within the framework of the molecular field theory taking into account the anisotropy of unstable sublattice. The magnetization curves of single crystal GdMn 2Ge 2 for the magnetic field parallel and perpendicular to the c axis at different temperatures are calculated. Field induced magnetic phase transitions in GdMn 2Ge 2 are discussed. Calculated H T magnetic phase diagrams are in fair agreement with experimental data.
基金the support from the Department of Science and Technology of Henan Province (No.082300410050)the Program for Science and Technology Innovation Talents in Universities of Henan Province (No.2008HASTIT008)
文摘The crystal and electronic structures of LaNi4.75Sn0.25 intermetallics and LaNi4.5Sn0.5Hy （y=2.0, 2.5） intermediate phase have been investigated by the fullpotential linearized augmented plane wave （FP-LAPW） method. Hydrogen occupation sites in LaNi4.5Sn0.5Hy have been determined based on Westlake＇s criterions： （1） the minimum hole radiuS is 0.04 nm; （2） the minimum H-H distance is 0.21 nm; as well as geometry optimizations and internal coordinates optimizations. We find that hydrogen atoms prefer to occupy the 12n＊, 6m, 12o, 6m＊ sites in LaNi4.5Sn0.5H2.0 and the 6m＊, 4h, 6m, 12o, 12n＊ sites in LaNi4.5Sn0.5H2.5. The specific coordinates of hydrogen atoms in LaNi4.5Sn0.5Hy are also determined. The results show that hydrogen atoms tend to keep away from tin atoms. The maximum hydrogen content decreases compared with LaNi5. The interactions between Sn and Ni with H play a dominate role in the stability of LaNi4.5Sn0.5-H system. Lattice expansion and increment of Fermi energy EF show that both Sn and H atoms decrease structural stability of these alloys.
文摘The influence of rare earth element Dy on martensitic transformation and magnetic properties of Co-Ni-Al alloy was studied.The results showed that the microstructure of the sample has a dual-phase structure（γ-phase and martensite）.The rare earth element Dy was segregated in Co-richγ-phase and took the place of Co after its addition into the Co-Ni-Al alloy.As Dy content increased to over 0.5at.%,the grain was refined and the rare earth intermetallic compounds Co5 Dy were precipitated inγ-phase.Meanwhile,one-step thermo-elastic martensitic transformation occurred in the sample,wherein the phase transformation temperature significantly increased with rising Dy content.The martensite had a tetragonal L10 structure with a（111）twinning plane.Furthermore,the sample exhibited obvious hysteresis behaviors in the magnetic hysteresis loops.In addition,the saturation magnetization,coercivity,retentivity and magnetocrystalline anisotropy were significantly enhanced owing to the bigger radius of Dy which took the place of Co in the alloy.
