Iron-rich compounds with the tetragonal ThMn12-type structure have the potential to meet current demands for rare-earth-lean permanent magnets with high energy density and operating temperatures of 150-200℃.However,w...Iron-rich compounds with the tetragonal ThMn12-type structure have the potential to meet current demands for rare-earth-lean permanent magnets with high energy density and operating temperatures of 150-200℃.However,while it is normal for magnet technology to lag behind the development of underlying magnetic material,this gap has always been unusually large for ThMn12-type magnets.The gap has widened further in recent years,as excellent combinations of intrinsic magnetic properties have been obtained in compounds synthesized with a smaller amount of structure-stabilizing elements(e.g.,SmFe11V or Sm0.8Zr0.2Fe9.2Co2.3Ti0.5)or with no such elements(i.e.,SmFe9.6Co2.4 thin films).The search for promising compounds continues-with increasing help coming from theoretical calculations.Unfortunately,progress in the development of magnets beyond polymer-bonded interstitially modified powders remains marginal.The introduction of lanthanum(La)was found to stabilize low-meltingtemperature minority phases in Sm(Fe,Ti)12 alloys,thus allowing for liquid-phase sintering for the first time.The high reactivity of La,however,has apparently undermined the development of coercivity(Hc).A controlled crystallization of the initially suppressed ThMn12-type phase makes"bulk"magnetic hardening possible,not only in Sm-Fe-V alloys(in which it has been known since the 1990s),but also is in La-added(Ce,Sm)(Fe,Ti)12 alloys.The properties of the bulk-hardened alloys,however,remain unsatisfactory.Mechanochemically synthesized(Sm,Zr)(Fe,Si)12 and(Sm,Zr)(Fe,Co,Ti)12 powders may become suitable for sintering into powerful fully dense magnets,although not before a higher degree of anisotropy in both alloys and a higher Hc in the latter alloy have been developed.展开更多
The effect of substitution of Mn on the structure and magnetic properties of HoFe 12- x Mn x (x =2 0, 3 0, 4 0 and 5 0) compounds was investigated. All the HoFe 12x Mn x compounds studied cry...The effect of substitution of Mn on the structure and magnetic properties of HoFe 12- x Mn x (x =2 0, 3 0, 4 0 and 5 0) compounds was investigated. All the HoFe 12x Mn x compounds studied crystallize in ThMn 12 type of structure. The lattice constants and unit cell volume increase monotonously with increasing Mn concentration. The Curie temperature and the moments of the transition metal sublattice of HoFe 12- x Mn x compounds decrease monotonously with increasing Mn content. A minimum appears at x =3 0 in the Mn concentration dependence of the saturation magnetization of HoFe 12- x Mn x compounds. A compensation point appears in the M(t) curve of the compound with x =4 0. The mean field constant n RT of HoFe 9Mn 3 was calculated.展开更多
The effect of Mn substitution for partial Fe in RFe 11Ti on structure and magnetic properties of compounds was researched. RFe 7Mn 4Ti samples (R=Y,Tb,Dy,Ho,Er) were prepared by means of vacuum arc-melting and s...The effect of Mn substitution for partial Fe in RFe 11Ti on structure and magnetic properties of compounds was researched. RFe 7Mn 4Ti samples (R=Y,Tb,Dy,Ho,Er) were prepared by means of vacuum arc-melting and subsequent vacuum annealing. The structure and magnetic properties of RFe 7Mn 4Ti compounds were investigated by X-ray powder diffraction and magnetic measurements. The following conclusions were obtained: all the RFe tMn 4Ti compounds crystallize in the ThMn 12-type structure. The lattice constants and the unit-cell volume changed with the increase of atomic number for R=Y, Tb, Dy, Ho, and Er. The compensation characters appear for the DyFe 7Mn 4Ti and HoFe 7Mn 4Ti compounds, and the compensation temperatures were about 123 K and 90 K, respectively. The Curie temperature, the saturation magnetization, and saturation moment of RFe 7Mn 4Ti compounds were given.展开更多
基金supported by the US Department of Energy,United States(DE-FG02-90ER45413)EU Horizon 2020 Program(686056–NOVAMAG)Ford Motor Company,United States.
文摘Iron-rich compounds with the tetragonal ThMn12-type structure have the potential to meet current demands for rare-earth-lean permanent magnets with high energy density and operating temperatures of 150-200℃.However,while it is normal for magnet technology to lag behind the development of underlying magnetic material,this gap has always been unusually large for ThMn12-type magnets.The gap has widened further in recent years,as excellent combinations of intrinsic magnetic properties have been obtained in compounds synthesized with a smaller amount of structure-stabilizing elements(e.g.,SmFe11V or Sm0.8Zr0.2Fe9.2Co2.3Ti0.5)or with no such elements(i.e.,SmFe9.6Co2.4 thin films).The search for promising compounds continues-with increasing help coming from theoretical calculations.Unfortunately,progress in the development of magnets beyond polymer-bonded interstitially modified powders remains marginal.The introduction of lanthanum(La)was found to stabilize low-meltingtemperature minority phases in Sm(Fe,Ti)12 alloys,thus allowing for liquid-phase sintering for the first time.The high reactivity of La,however,has apparently undermined the development of coercivity(Hc).A controlled crystallization of the initially suppressed ThMn12-type phase makes"bulk"magnetic hardening possible,not only in Sm-Fe-V alloys(in which it has been known since the 1990s),but also is in La-added(Ce,Sm)(Fe,Ti)12 alloys.The properties of the bulk-hardened alloys,however,remain unsatisfactory.Mechanochemically synthesized(Sm,Zr)(Fe,Si)12 and(Sm,Zr)(Fe,Co,Ti)12 powders may become suitable for sintering into powerful fully dense magnets,although not before a higher degree of anisotropy in both alloys and a higher Hc in the latter alloy have been developed.
文摘The effect of substitution of Mn on the structure and magnetic properties of HoFe 12- x Mn x (x =2 0, 3 0, 4 0 and 5 0) compounds was investigated. All the HoFe 12x Mn x compounds studied crystallize in ThMn 12 type of structure. The lattice constants and unit cell volume increase monotonously with increasing Mn concentration. The Curie temperature and the moments of the transition metal sublattice of HoFe 12- x Mn x compounds decrease monotonously with increasing Mn content. A minimum appears at x =3 0 in the Mn concentration dependence of the saturation magnetization of HoFe 12- x Mn x compounds. A compensation point appears in the M(t) curve of the compound with x =4 0. The mean field constant n RT of HoFe 9Mn 3 was calculated.
文摘The effect of Mn substitution for partial Fe in RFe 11Ti on structure and magnetic properties of compounds was researched. RFe 7Mn 4Ti samples (R=Y,Tb,Dy,Ho,Er) were prepared by means of vacuum arc-melting and subsequent vacuum annealing. The structure and magnetic properties of RFe 7Mn 4Ti compounds were investigated by X-ray powder diffraction and magnetic measurements. The following conclusions were obtained: all the RFe tMn 4Ti compounds crystallize in the ThMn 12-type structure. The lattice constants and the unit-cell volume changed with the increase of atomic number for R=Y, Tb, Dy, Ho, and Er. The compensation characters appear for the DyFe 7Mn 4Ti and HoFe 7Mn 4Ti compounds, and the compensation temperatures were about 123 K and 90 K, respectively. The Curie temperature, the saturation magnetization, and saturation moment of RFe 7Mn 4Ti compounds were given.
