Carrier core material, and electrophotographic development carrier and electrophotographic developer using same

1 . A carrier core material comprising ferrite particles,

wherein a composition of the ferrite particle has the formula M X Fe 3-x O 4 , wherein M is Mn and x is defined such that the composition contains 35 mole percent or more and 55 mole percent or less of MnO and 45 mole percent or more and 65 mole percent or less of Fe 2 O 3 , and part thereof is substituted for 0.1 mole percent or more and 1.0 mole percent or less of SrO and 0.1 mole percent or more and 1.0 mole percent or less of SnO,

a volume moment mean D [4, 3] of O. Bluntness measured with an injection type image analysis particle size distribution meter is equal to or greater than 65% and equal to or less than 80%, and

a volume moment mean D [4, 3] of ISO Roundness is equal to or greater than 80% and equal to or less than 86%.

2 . The carrier core material according to claim 1 ,

wherein a saturation magnetization σ S is equal to or greater than 75 Am 2 /kg and equal to or less than 88 Am 2 /kg.

3 . The carrier core material according to claim 1 ,

wherein a pore volume is equal to or less than 0.01 cm 3 /g.

4 . An electrophotographic development carrier,

wherein a surface of the carrier core material according to claim 1 is coated with a resin.

5 . An electrophotographic developer comprising:

the electrophotographic development carrier according to claim 4 ; and

a toner.