At a laboratory inside a Google data center in Mayes County , Oklahoma, researchers spent the fall of 2019 disassembling old hard disk drives by hand in order to extract a 2-inch-long component known as the magnet assembly. Consisting of two powerful rare earth magnets, the magnet assembly is a critical muscle within the hard drive, controlling an actuator arm that allows the device to read and write data.
Source: Can you recycle a hard drive? Google is quietly trying to find out