Abstract: A carrier core material is represented by a composition formula MXFe3-XO4 (where M is at least one type of metal element selected from Mg, Mn, Ca, Ti, Cu, Zn and Ni, 0<X<1), in which part of M and/or Fe is substituted with Sr and formed of ferrite particles, and in the carrier core material, a Sr content is equal to or more than 2500 ppm but equal to or less than 12000 ppm, the amount of Sr eluted with pure water at a temperature of 25° C. is equal to or less than 50 ppm, an apparent density is equal to or more than 1.85 g/cm3 but equal to or less than 2.25 g/cm3 and magnetization ?1k when a magnetic field of 79.58×103 A/m (1000 oersteds) is applied is equal to or more than 63 Am2/kg but equal to or less than 75 Am2/kg.

Abstract: A carrier core material formed with ferrite particles, the skewness Rsk of the particle is equal to or more than ?0.40 but equal to or less than ?0.20, and the kurtosis Rku of the particle is equal to or more than 3.20 but equal to or less than 3.50. Here, the maximum height Rz of the particle is equal to or more than 2.20 ?m but equal to or less than 3.50 ?m. Moreover, the ferrite particle contains at least either of Mn and Mg elements. In this way, cracking or chipping in a concave-convex portion of a particle surface is unlikely to occur, and moreover, the amount of coating resin used can be reduced without properties such as electrical resistance being lowered.

Abstract: A carrier core material is represented by a composition formula MXFe3-XO4 (where M is at least one type of metal element selected from Mg, Mn, Ca, Ti, Cu, Zn and Ni, 0<X<1), in which part of M and/or Fe is substituted with Sr and formed of ferrite particles, and in the carrier core material, a Sr content is equal to or more than 2500 ppm but equal to or less than 12000 ppm, the amount of Sr eluted with pure water at a temperature of 25° C. is equal to or less than 50 ppm, an apparent density is equal to or more than 1.85 g/cm3 but equal to or less than 2.25 g/cm3 and magnetization ?1k when a magnetic field of 79.58×103 A/m (1000 oersteds) is applied is equal to or more than 63 Am2/kg but equal to or less than 75 Am2/kg.

Abstract: A carrier core material formed with ferrite particles, the skewness Rsk of the particle is equal to or more than ?0.40 but equal to or less than ?0.20, and the kurtosis Rku of the particle is equal to or more than 3.20 but equal to or less than 3.50. Here, the maximum height Rz of the particle is equal to or more than 2.20 ?m but equal to or less than 3.50 ?m. Moreover, the ferrite particle contains at least either of Mn and Mg elements. In this way, cracking or chipping in a concave-convex portion of a particle surface is unlikely to occur, and moreover, the amount of coating resin used can be reduced without properties such as electrical resistance being lowered.

Abstract: There are provided ferrite particles in which Mn ferrite is used as the main phase and which contain Sr ferrite, where the degree of projections and recesses in the surface of the particles falls within a range of 2.5 to 4.5 ?m, and the standard deviation of the size of grains appearing on the surface of the particles falls within a range of 1.5 to 3.5 ?m. In this way, a coating resin is left on the surface of the particles even after long-term use and thus a decrease in the charging property is reduced.

Abstract: There are provided ferrite particles in which Mn ferrite is used as the main phase and which contain Sr ferrite, where the degree of projections and recesses in the surface of the particles falls within a range of 2.5 to 4.5 ?m, and the standard deviation of the size of grains appearing on the surface of the particles falls within a range of 1.5 to 3.5 ?m. In this way, a coating resin is left on the surface of the particles even after long-term use and thus a decrease in the charging property is reduced.