The hard drive magnets are very strong magnets and are made from an alloy of neodymium, iron and boron to form the Nd2Fe14B tetragonal crystalline.
The hard drive magnets are called neodymium magnets and can actually be sold on ebay for some money because people use the magnets from hard drives for many other things.
I have a few myself I saved from old hard drives and they're strong magnets.