A soft magnetic powder contains a particle having a composition represented by Fe.sub.xCu.sub.aNb.sub.b(Si.sub.1-yB.sub.y).sub.100-x-a-b, and 0.3≤a≤2.0, 2.0≤b≤4.0, and 75.5≤x≤79.5, and y is a number satisfying f(x)≤y≤0.99, and f(x)=(4×10.sup.−34) x.sup.17.56. The particle includes a crystal grain having a grain size of 1 nm to 30 nm, a Cu segregation portion, and a crystal grain boundary. A content proportion of the crystal grain is 30% or more. When the Cu segregation portion positioned in a surface layer portion and having a grain size of 2 nm to 10 nm is referred to as a first Cu segregation portion, and the Cu segregation portion positioned in an inner portion and having a grain size of 2 nm to 7 nm is referred to as a second Cu segregation portion, a number proportion of the first Cu segregation portion is 80% or more, a number proportion of the second Cu segregation portion is 80% or more, and the number of the second Cu segregation portion is twice or more the number of the first Cu segregation portion.

A soft magnetic powder contains a particle having a composition represented by Fe.sub.xCu.sub.aNb.sub.b(Si.sub.1-yB.sub.y).sub.100-x-a-b, and 0.3≤a≤2.0, 2.0≤b≤4.0, and 75.5≤x≤79.5, and y is a number satisfying f(x)≤y≤0.99, and f(x)=(4×10.sup.−34) x.sup.17.56. The particle includes a crystal grain having a grain size of 1 nm to 30 nm, a Cu segregation portion, and a crystal grain boundary. A content proportion of the crystal grain is 30% or more. When the Cu segregation portion positioned in a surface layer portion and having a grain size of 2 nm to 10 nm is referred to as a first Cu segregation portion, and the Cu segregation portion positioned in an inner portion and having a grain size of 2 nm to 7 nm is referred to as a second Cu segregation portion, a number proportion of the first Cu segregation portion is 80% or more, a number proportion of the second Cu segregation portion is 80% or more, and the number of the second Cu segregation portion is twice or more the number of the first Cu segregation portion.

The present invention relates to an R-T-B sintered magnet and a preparation method thereof. The sintered magnet includes a grain boundary region T1, a shell layer region T2 and an R.sub.2Fe.sub.14B grain region T3; at 10 μm to 60 μm from a surface of the sintered magnet toward a center thereof, an area ratio of the shell layer region T2 to the R.sub.2Fe.sub.14B grain region T3 is 0.1 to 0.3, and a thickness of the shell layer region T2 is 0.5 μm to 1.2 μm; and an average coating percent of the shell layer region T2 on the R.sub.2Fe.sub.14B grain region T3 is 80% or more. In the present invention, by optimizing a preparation process and a microstructure of a traditional rare earth permanent magnet, diffusion efficiency of heavy rare earth in the magnet is improved, such that coercivity of the magnet is greatly improved, and manufacturing cost is reduced.

The present invention relates to an R-T-B sintered magnet and a preparation method thereof. The sintered magnet includes a grain boundary region T1, a shell layer region T2 and an R.sub.2Fe.sub.14B grain region T3; at 10 μm to 60 μm from a surface of the sintered magnet toward a center thereof, an area ratio of the shell layer region T2 to the R.sub.2Fe.sub.14B grain region T3 is 0.1 to 0.3, and a thickness of the shell layer region T2 is 0.5 μm to 1.2 μm; and an average coating percent of the shell layer region T2 on the R.sub.2Fe.sub.14B grain region T3 is 80% or more. In the present invention, by optimizing a preparation process and a microstructure of a traditional rare earth permanent magnet, diffusion efficiency of heavy rare earth in the magnet is improved, such that coercivity of the magnet is greatly improved, and manufacturing cost is reduced.

Provided is an Fe-based nanocrystalline alloy powder. The Fe-based nanocrystalline alloy powder has a chemical composition, excluding inevitable impurities, represented by a composition formula of Fe.sub.aSi.sub.bB.sub.cP.sub.dCu.sub.eM.sub.f, where the M in the composition formula is at least one element selected from the group consisting of Nb, Mo, Zr, Ta, W, Hf, Ti, V, Cr, Mn, C, Al, S, O, and N, 79 at %≤a≤84.5 at %, 0 at %≤b<6 at %, 0 at %<c≤10 at %, 4 at %<d≤11 at %, 0.2 at %≤e≤0.53 at %, 0 at %≤f≤4 at %, a+b+c+d+e+f=100 at %, a degree of crystallinity is more than 10% by volume, and an Fe crystallite diameter of the Fe-based nanocrystalline alloy powder is 50 nm or less.

Provided is an Fe-based nanocrystalline alloy powder. The Fe-based nanocrystalline alloy powder has a chemical composition, excluding inevitable impurities, represented by a composition formula of Fe.sub.aSi.sub.bB.sub.cP.sub.dCu.sub.eM.sub.f, where the M in the composition formula is at least one element selected from the group consisting of Nb, Mo, Zr, Ta, W, Hf, Ti, V, Cr, Mn, C, Al, S, O, and N, 79 at %≤a≤84.5 at %, 0 at %≤b<6 at %, 0 at %<c≤10 at %, 4 at %<d≤11 at %, 0.2 at %≤e≤0.53 at %, 0 at %≤f≤4 at %, a+b+c+d+e+f=100 at %, a degree of crystallinity is more than 10% by volume, and an Fe crystallite diameter of the Fe-based nanocrystalline alloy powder is 50 nm or less.

A dust core contains a powder of a crystalline magnetic material powder and a powder of an amorphous magnetic material. The sum of the content of the crystalline magnetic material powder and the content of the amorphous magnetic material powder is 83 mass percent or more. The mass ratio of the content of the crystalline magnetic material powder to the sum of the content of the crystalline magnetic material powder and the content of the amorphous magnetic material powder is 20 mass percent or less. The median diameter D50 of the amorphous magnetic material powder is greater than or equal to the median diameter D50 of the crystalline magnetic material powder.

A dust core contains a powder of a crystalline magnetic material powder and a powder of an amorphous magnetic material. The sum of the content of the crystalline magnetic material powder and the content of the amorphous magnetic material powder is 83 mass percent or more. The mass ratio of the content of the crystalline magnetic material powder to the sum of the content of the crystalline magnetic material powder and the content of the amorphous magnetic material powder is 20 mass percent or less. The median diameter D50 of the amorphous magnetic material powder is greater than or equal to the median diameter D50 of the crystalline magnetic material powder.

A powder for dust core used for a dust core includes a plurality of crystal grains, and the powder has at least two maximal values when a number ratio that is a ratio of the number of the crystal grains at each crystal grain diameter to the number of the crystal grains each crystal grain diameter of which has been measured is plotted with respect to each crystal grain diameter of the crystal grains.

A powder for dust core used for a dust core includes a plurality of crystal grains, and the powder has at least two maximal values when a number ratio that is a ratio of the number of the crystal grains at each crystal grain diameter to the number of the crystal grains each crystal grain diameter of which has been measured is plotted with respect to each crystal grain diameter of the crystal grains.