Magnetic Imaging of Bits in Hard Disk Media using Lorentz Transmission Electron Microscopy

We are living in a time of big data where over an exabyte (10⁹ GB) of new information is generated every day. One of the most economical means to store large amounts of data is hard disk drives (HDDs). In HDDs, information is stored as magnetic bits. In current commercial HDDs, each bit is less than 50 nm long, but to increase the storage density an individual bit has to get even smaller. 

In this talk, I explore the magnetic imaging capability of the transmission electron microscope (TEM) to characterize individual bits. First, I demonstrate the feasibility of a correlative study between the magnetic bits and the HDD materials’ structure in the TEM, using a combination of Lorentz and bright field imaging. To image magnetic fields in modern HDDs with perpendicular recording technology, I establish an experimental method of tilting the specimen relative to the electron beam. In the second part, I investigate next generation heat-assisted magnetic recording media HDDs. For this sample, a focused ion beam was used to extract a cross-sectional specimen from a single row of bits. The Lorentz imaging technique was again applied to successfully resolve individual bits.