| 摘要 |
A powder for use in the lower layer of a coating magnetic recording medium, comprising acicular particles with a mean major axis length in a range of from 0.01 to 0.5 mum and a mean minor axis length in a range of from 0.01 to 0.05 mum, provided that the acicular particles are flat acicular particles which, when cut in a direction perpendicular to the major axis, uniformly exhibit a cross section having a larger width to smaller width ratio of greater than 1, and that the quantity of discharged H2O at 100° C. is in a range of from 0.1 to 2.0% by weight.
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