hard disc vs magnetic disc

hard disc and magnetic disc both are nouns.

Word	Noun	Adjective	Verb	Adverb
hard disc	Yes	No	No	No
magnetic disc	Yes	No	No	No

As nouns, magnetic disc is a hypernym of hard disc; that is, magnetic disc is a word with a broader meaning than hard disc:

hard disc: a rigid magnetic disk mounted permanently in a drive unit
magnetic disc: (computer science) a memory device consisting of a flat disk covered with a magnetic coating on which information is stored

Other hypernyms of hard disc include disc, disk, magnetic disk.

hard disc (noun)	magnetic disc (noun)
a rigid magnetic disk mounted permanently in a drive unit	(computer science) a memory device consisting of a flat disk covered with a magnetic coating on which information is stored