Patent ID: 8303837

Claim:
A magnet roll, at least one magnetic pole portion of which is made of a bonded magnet comprising ferrite powder and a binder, said ferrite powder having an M-type ferrite structure, comprising Ca, an R element that is at least one of rare earth elements and indispensably includes La, Ba, Fe and Co as indispensable elements, and having a composition represented by the following general formula: Ca 1-x-y R x Ba y Fe 2n-z Co z (by atomic ratio), wherein (1−x−y), x, y, z and n represent the contents of Ca, the R element, Ba and Co, and a molar ratio, meeting 0.3≦1 −x−y≦ 0.65, 0.2 ≦x≦ 0.65, 0.001 ≦y≦ 0.2, 0.03 ≦z≦ 0.65, 4 ≦n≦ 7, and 1 −x−y>y.