Which type of ferromagnetic material is used in coating magnetic tapes in a cassette player?whta is called invar?

Dear Ashwathy,

Ceramics are used for coating magnetic tapes in a cassette player or for building memory stores in a modern computer. Ceramics are specially treated barium-iron oxides and are also called ferrites.

Invar, also known generically as FeNi36 (64FeNi in the US), is a nickel steel alloy notable for its uniquely low coefficient of thermal expansion (CTE or α). The name, Invar, comes from the word invariable, referring to its lack of expansion or contraction with temperature changes.^[1]

It was invented in 1896 by Swiss scientist Charles Édouard Guillaume. He received the Nobel Prize in Physics in 1920 for this discovery, which enabled improvements in scientific instruments.^[2]

Invar is a registered trademark^[3] of ArcelorMittal.^[4] FeNi36 is also manufactured by Japanese companies such as Nippon Yakin Kogyo.

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