To provide a ferrite sintered magnet having a high residual magnetic flux density (Br), a high coercive force (HcJ), a good production stability, and also able to produce at a low cost. The ferrite sintered magnet includes a hexagonal M-type ferrite including A, R, Fe, and Co in an atomic ratio of A.sub.1-xR.sub.x(Fe.sub.12-yCo.sub.y).sub.zO.sub.19. A is at least one selected from Sr, Ba, and Pb. R is La only or La and at least one selected from rare earth elements. 0.14≤x≤0.22, 11.60≤(12-y)z≤11.99, and 0.13≤yz≤0.17 are satisfied. 0.30≤Mc≤0.63 is satisfied in which Mc is CaO content (mass %) converted from a content of Ca included in the ferrite sintered magnet.

To provide a ferrite sintered magnet having a high residual magnetic flux density (Br) and a high coercive force (HcJ), and also able to produce at a low cost. The ferrite sintered magnet includes a hexagonal M-type ferrite including A, R, Fe, and Co in an atomic ratio of A.sub.1-xR.sub.x(Fe.sub.12-yCo.sub.y).sub.zO.sub.19. A is at least one selected from Sr, Ba, and Pb. R is La only or La and at least one selected from rare earth elements. 0.13≤x≤0.23, 10.80≤(12−y)z≤12.10, and 0.13≤yz≤0.20 are satisfied.

A magnetic nanoparticle, and composites thereof, comprising a ternary host compound comprising a transition metal oxide of size 2-30 nm having two transition metal dopants atom incorporated therein, such that the nanoparticle is converted from superparamagnetic or weak ferromagnetic to strong ferromagnetic material. The strong permanent magnets are formed from non-rare earth materials. The composite material can also include undoped nanoparticles.

A magnetic nanoparticle, and composites thereof, comprising a ternary host compound comprising a transition metal oxide of size 2-30 nm having two transition metal dopants atom incorporated therein, such that the nanoparticle is converted from superparamagnetic or weak ferromagnetic to strong ferromagnetic material. The strong permanent magnets are formed from non-rare earth materials. The composite material can also include undoped nanoparticles.

Disclosed herein are embodiments of composite hexagonal ferrite materials formed from a combination of Y phase and Z phase hexagonal ferrite materials. Advantageously, embodiments of the material can have a high resonant frequency as well as a high permeability. In some embodiments, the materials can be useful for magnetodielectric antennas.

Disclosed herein are embodiments of composite hexagonal ferrite materials formed from a combination of Y phase and Z phase hexagonal ferrite materials. Advantageously, embodiments of the material can have a high resonant frequency as well as a high permeability. In some embodiments, the materials can be useful for magnetodielectric antennas.

A magnetic core material for electrophotographic developer, satisfying a value of Expression (1): a+b×10+c+d+e+f, being from 200 to 1,400, when an amount of fluorine ion is denoted by a (ppm), an amount of chlorine ion is denoted by b (ppm), an amount of bromide ion is denoted by c (ppm), an amount of nitrite ion is denoted by d (ppm), an amount of nitrate ion is denoted by e (ppm), and an amount of sulfate ion is denoted by f (ppm), which are measured by combustion ion chromatography; and having a pore volume of from 30 to 100 mm.sup.3/g.

A magnetic core material for electrophotographic developer, satisfying a value of Expression (1): a+b×10+c+d+e+f, being from 200 to 1,400, when an amount of fluorine ion is denoted by a (ppm), an amount of chlorine ion is denoted by b (ppm), an amount of bromide ion is denoted by c (ppm), an amount of nitrite ion is denoted by d (ppm), an amount of nitrate ion is denoted by e (ppm), and an amount of sulfate ion is denoted by f (ppm), which are measured by combustion ion chromatography; and having a pore volume of from 30 to 100 mm.sup.3/g.

A ferrite sintered magnet 100 comprises M-type ferrite crystal grains 4 and multiple-crystal grain boundaries 6b surrounded by three or more of the M-type ferrite crystal grains 4. The ferrite sintered magnet 100 contains at least Fe, Ca, B, and Si, and contains 0.005 to 0.9 mass % of B in terms of B.sub.2O.sub.3. The multiple-crystal grain boundaries 6b contain Si and Ca, and in a case where the molar ratio of Ca to Si in the multiple-crystal grain boundaries 6b is represented by (Ca/Si).sub.G, the following formula is satisfied.

0.1<(Ca/Si).sub.G<0.9

A ferrite sintered magnet 100 comprises M-type ferrite crystal grains 4 and multiple-crystal grain boundaries 6b surrounded by three or more of the M-type ferrite crystal grains 4. The ferrite sintered magnet 100 contains at least Fe, Ca, B, and Si, and contains 0.005 to 0.9 mass % of B in terms of B.sub.2O.sub.3. The multiple-crystal grain boundaries 6b contain Si and Ca, and in a case where the molar ratio of Ca to Si in the multiple-crystal grain boundaries 6b is represented by (Ca/Si).sub.G, the following formula is satisfied.

0.1<(Ca/Si).sub.G<0.9