Provided are a magnetic core material for electrophotographic developer and a carrier for electrophotographic developer, which are excellent in charge characteristics and strength and with which a satisfactory image free from defects can be obtained, and a developer containing the carrier. A magnetic core material for electrophotographic developer, having a sulfur component content of from 50 to 700 ppm in terms of a sulfate ion and a BET specific surface area of from 0.06 to 0.25 m.sup.2/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.

Provided is a magnetic toner having a toner particle containing a binder resin and a magnetic body, wherein the binder resin contains a polymer A having a first monomer unit and a second monomer unit, the first polymerizable monomer is at least one selected from the group consisting of the (meth)acrylic acid esters having C.sub.18-36 alkyl groups, a content of the first monomer unit and a content of the second monomer unit based on the total moles of all monomer units in the polymer A are respectively 5.0 to 60.0 mol % and 20.0 to 95.0 mol %, and assuming that an SP value of the first monomer unit and the second monomer unit are taken as SP.sub.11 (J/cm.sup.3).sup.0.5 and SP.sub.21(J/cm.sup.3).sup.0.5, respectively, 3.00≤(SP.sub.21−SP.sub.11)≤25.00 is satisfied, and an oil absorption of the magnetic body is 5 to 40 ml/100 g.

A magnetic carrier including a magnetic carrier particle having a magnetic core particle and a coating layer of an organosilicon polymer on a surface of the magnetic core particle, wherein the organosilicon polymer has the structure given by formula (T3) below; in .sup.29Si-NMR measurement of the THF-insoluble matter of the organosilicon polymer, the ratio ST3 of the peak area for the structure given by formula (T3) to the total peak area for the organosilicon polymer is at least 0.05; and in the roughness curve measured on the magnetic carrier particle, the mean width (RSm) of the roughness curve elements of the magnetic carrier particle, and the ratio (/RSm) to this RSm of the standard deviation of the width of the region where one period of a protrusion and a recess occurs, are in prescribed ranges.

RSi(O.sub.1/2).sub.3(T3)

R in the formula represents a prescribed substituent.

A magnetic toner comprising a magnetic toner particle including a binder resin, a magnetic body and a crystalline polyester, wherein a storage elastic modulus E(40) [Pa] at 40 C. and a storage elastic modulus E(85) [Pa] at 85 C., which are obtained in a powder dynamic viscoelasticity measurement of the magnetic toner, satisfy the following formulas (1) to (3).
E(40)6.010.sup.9(1)
E(85)5.510.sup.9(2)
[E(40)E(85)]100/E(40)40(3)

A toner includes toner particles. The toner particles each include a toner mother particle. The toner mother particles contain a binder resin and a magnetic powder. The binder resin includes a polyester resin, a vinyl resin, and a block polymer. The block polymer includes a polyester portion, a vinyl polymer portion, and a linker that links the polyester portion and the vinyl polymer portion. The linker is derived from a specific compound having a vinyl group and at least one of a carboxy group and an alcoholic hydroxyl group. The magnetic powder has an octahedral structure.

A magnetic toner comprising a magnetic toner particle including a binder resin, a magnetic body and a crystalline polyester, wherein the dielectric loss tangent at 100 kHz is 1.010.sup.2 or more, a variation coefficient CV3 of an occupied area ratio of the magnetic body when a cross section of the magnetic toner particle is divided by a square grid having a side of 0.8 m in cross-sectional observation of the magnetic toner particle using a transmission electron microscope TEM is from 30.0% to 80.0%, and where a storage elastic modulus of the magnetic toner at 40 C. is taken as E(40) [Pa] and a storage elastic modulus of the magnetic toner at 85 C. is taken as E(85) [Pa], the following formulas (1) and (2) are satisfied:
E(85)5.510.sup.9(1)
[E(40)E(85)]100/E(40)30(2).

A toner comprising a toner particle including a binder resin and a magnetic body, wherein in cross-sectional observation of the toner with a transmission electron microscope, where an area percentage occupied by the magnetic body in a region of 200 nm or less from a contour of a cross section of the toner particle to a centroid of the cross section is taken as A1, and an area percentage occupied by the magnetic body in a region of from 200 nm to 400 nm from the contour of the cross section of the toner particle to the centroid of the cross section is taken as A2, the area percentage A1 is from 38% to 85%, the area percentage A2 is from 0% to 37%, and a ratio A2/A1 of the area percentage A2 to the area percentage A1 is from 0 to 0.75.

A magnetic toner comprising a magnetic toner particle including a binder resin, a magnetic body and a crystalline polyester, wherein a storage elastic modulus E(40) [Pa] at 40 C. and a storage elastic modulus E(85) [Pa] at 85 C., which are obtained in a powder dynamic viscoelasticity measurement of the magnetic toner, satisfy the following formulas (1) to (3).

E(40)6.010.sup.9 (1)

E(85)5.510.sup.9 (2)

[E(40)E(85)]100/E(40) (3)

A magnetic toner comprising a magnetic toner particle including a binder resin, a magnetic body and a crystalline polyester, wherein the dielectric loss tangent at 100 kHz is 1.010.sup.2 or more, a variation coefficient CV3 of an occupied area ratio of the magnetic body when a cross section of the magnetic toner particle is divided by a square grid having a side of 0.8 m in cross-sectional observation of the magnetic toner particle using a transmission electron microscope TEM is from 30.0% to 80.0%, and where a storage elastic modulus of the magnetic toner at 40 C. is taken as E(40) [Pa] and a storage elastic modulus of the magnetic toner at 85 C. is taken as E(85) [Pa], the following formulas (1) and (2) are satisfied:

E(85)5.510.sup.9 (1)

[E(40)E(85)]100/E(40)30 (2)