Tdk Corporation

Ricoh Company, Ltd.

Ken Satoh

Hitoshi Ohkubo

Kentaro Saito

Kyohei Tonoyama

Miyuki Asai

Takahiro Yamazaki

Yasuhiro Hattori

Hidenori Shindoh

A magnetic core includes a metal magnetic powder, which has a large size powder, an intermediate size powder, and a small size powder. A particle size of the large size powder is 10 &#x3bc;m or more and 60 &#x3bc;m or less. A particle size of the intermediate size powder is 2.0 &#x3bc;m or more and less than 10 &#x3bc;m. A particle size of the small size powder is 0.1 &#x3bc;m or more and less than 2.0 &#x3bc;m. The large size powder, the intermediate size powder, and the small size powder have an insulation coating. When A1 represents an average insulation coating thickness of the large size powder, A2 represents an average insulation coating thickness of the intermediate size powder, A3 represents an average insulation coating thickness of the small size powder, A3 is 30 nm or more and 100 nm or less, A3/A1&#x2265;1.3, and A3/A2&#x2265;1.0.

Magnetic core and coil component

A magnetic core and a coil component with excellent permeability, core loss, DC superimposition property, and withstand voltage. A magnetic core has a metal magnetic powder containing resin including a metal magnetic powder. The metal magnetic powder includes a large size powder, an intermediate size powder, and a small size powder. A particle size of the large size powder is 10 &#x3bc;m or more and 60 &#x3bc;m or less. A particle size of the intermediate size powder is 2.0 &#x3bc;m or more and less than 10 &#x3bc;m. A particle size of the small size powder is 0.1 &#x3bc;m or more and less than 2.0 &#x3bc;m. The large size powder includes a nano crystal. A ratio of the large size powder existing with respect to the metal magnetic powder is 39% or more and 91% or less in terms of an area ratio in a cross section of the magnetic core.

An image forming apparatus includes a plurality of erase information each showing whether or not to erase data for each of a plurality of divided areas into which the hard disk is divided, group erase information showing groups grouping the erase information, and erase count information determined based on the group erase information. Based on the erase count information whether or not there is a divided area to erase, the divided area is erased.

Image forming apparatus, erasing method, and hard disk management method

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Tokyo, Japan

Ken Satoh