The present invention provides a ferrite particle containing: a ferrite particle body having a spinel crystal structure belonging to a space group Fd-3m and having a spinel composition represented by the following formula (1); and a coating layer having a spinel crystal structure belonging to the space group Fd-3m and coating a surface of the ferrite particle body, in which the coating layer is a layer obtained by subjecting the ferrite represented by the following formula (1) to a heat treatment, and a content ratio of the coating layer in the ferrite particle obtained by subjecting a powder X-ray diffraction pattern to Rietveld analysis is 5 mass % or more and 35 mass % or less, and the ferrite particle satisfies a specific formula (2). The present invention also provides a carrier for an electrophotographic developer.

A carrier core material includes, a main component, a material represented by a composition formula Mn.sub.XM.sub.YFe.sub.3(X+Y)O.sub.4 (where M is selected from Mg, Ti, Cu, Zn and Ni, 0<X, 0Y, 0<X+Y<1), in which 0.1 to 1.0 mol % of at least one of Sr element and Ca element is contained as the total amount by conversion to SrO or CaO and in which the frequency of a grain whose length RSm is equal or more than 8.0 m among grains appearing on the surface of particles of the carrier core material is equal to or less than 2.0 number percent. In this way, the degradation of a carrier caused by long-term use such as the separation of a coating resin is significantly reduced, stable charging performance is maintained and the cracking or chipping of the particles is reduced.

An electrostatic charge image developer contains a toner including toner particles that contain a binder resin and a carrier including magnetic particles and a resin layer that adheres to a surface of the magnetic particles, in which, in a dynamic viscoelasticity measurement of the toner, in a case where a loss tangent tan? at a temperature of 90? C. and a strain of 1% is represented by D1 (90), a loss tangent tan? at a temperature of 90? C. and a strain of 50% is represented by D50 (90), a loss tangent tan? at a temperature of 150? C. and a strain of 1% is represented by D1 (150), and a loss tangent tan? at a temperature of 150? C. and a strain of 50% is represented by D50 (150), each of D1 (90), D50 (90), D1 (150), and D50 (150) is 0.5 or more and 2.5 or less, a value of D50 (150)?D1 (150) is less than 1.5, and a value of D50 (90)?D1 (90) is less than 1.0, and in the surface of the magnetic particles, an average unevenness interval Sm and an arithmetic mean roughness Ra satisfy 0.5 ?m? Sm?2.5 ?m and 0.3 ?m? Ra?1.2 ?m.

There is provided a toner set including a yellow toner, a cyan toner and a magenta toner, the toners each comprising an external additive and colored resin particles comprising a binder resin, a colorant and a charge control agent. An absolute value of an average of q/d for any of the yellow, cyan and magenta toners is expressed by charge amount q (fC) and particle diameter d (m). It is obtained by measurement using an electric field detachment-type charge amount distribution measurement device. It is in a range of 2.0 to 6.5 fC/10 m, and a standard deviation (SD) of q/d is 13 fC/10 m or less. A difference between average values of q/d for any two of the yellow, cyan and magenta toners is 2.0 fC/10 m or less. A difference (SD) between standard deviations of q/d for the two toners is 5.0 fC/10 m or less.

A magnetic carrier having a ferrite-type core material and a resin coat layer present on the surface of the ferrite-type core material, wherein the ferrite-type core material contains a magnetic ferrite-type core material particle and an amino group-bearing primer compound; the resin coat layer contains a coating resin A that is a polymer of monomer containing a (meth)acrylate ester having an alicyclic hydrocarbon group; the content of the amino group-bearing primer compound in the ferrite-type core material and the content of the resin coat layer in the magnetic carrier are within the prescribed range.

A carrier for developing electrostatic latent images is provided. The carrier includes a magnetic core particle and a resin layer coating a surface of the magnetic core particle. The resin layer includes a particulate material A having a volume average particle diameter (a) and a particulate material B having a volume average particle diameter (b). The volume average particle diameter (a) of the particulate material A is the largest among volume average particle diameters of all particulate materials included in the resin layer, and an inequation 100(a)/(b)5 is satisfied. The particulate material A is barium sulfate.

A carrier core material is represented by a composition formula M.sub.xFe.sub.3-xO.sub.4 (where M is Mn and/or Mg, and X is a total of Mn and Mg and is a substitution number of Fe by Mn and Mg, 0<X1), in which 5 to 20 number percent of bound particles where 2 to 5 spherical particles are bound together are contained and in which the maximum peak-to-trough depth Rz of the surface of normal spherical particles other than the bound particles is equal to or more than 1.5 m but equal to or less than 2.1 m. In this way, it is possible to increase the amount of toner supplied to a development region, and the surface of a photosensitive member is prevented from being scratched by a magnetic brush.

There is provided a toner set including a yellow toner, a cyan toner and a magenta toner, the toners each comprising an external additive and colored resin particles comprising a binder resin, a colorant and a charge control agent. An absolute value of an average of q/d for any of the yellow, cyan and magenta toners is expressed by charge amount q (fC) and particle diameter d (m). It is obtained by measurement using an electric field detachment-type charge amount distribution measurement device. It is in a range of 2.0 to 6.5 fC/10 m, and a standard deviation (SD) of q/d is 13 fC/10 m or less. A difference between average values of q/d for any two of the yellow, cyan and magenta toners is 2.0 fC/10 m or less. A difference (SD) between standard deviations of q/d for the two toners is 5.0 fC/10 m or less.

A carrier core material is represented by a composition formula M.sub.xFe.sub.3-xO.sub.4 (where M is Mn and/or Mg, and X is a total of Mn and Mg and is a substitution number of Fe by Mn and Mg, 0<X1), in which 5 to 20 number percent of bound particles in which 2 to 5 spherical particles are bound together are contained, and in which the absolute value of a difference between lattice constants before and after milling which are calculated from a peak position of plane indices in a powder X-ray diffraction pattern is equal to or less than 0.005. In this way, it is possible to increase the amount of toner supplied to a development region, and even when cracking or chipping occurs in the carrier core material, an image failure such as black spots or white spots is prevented from being generated.

An electrostatic charge image developer contains: a toner containing a toner particle and an external additive; and a carrier containing a magnetic particle and a resin layer covering the magnetic particle; and the toner particle has a surface property index value of 1.0 or more and less than 2.0; and the carrier has a surface having a ratio B/A of a surface area B to a plane view area A of 1.020 or more and 1.100 or less, the plane view area A and the surface area B being obtained by three-dimensional analysis of the surface of the carrier.