HAMR-based HDDs will use laser thermal assistance to first heat the platter to allow much higher storage density without having negative effects on read- and write-ability nor stability.
Capacities of modern hard drives are – among other things – constrained by the physical size of “pitches” on hard disk drives media required to store a single bit of information. Heat-assisted magnetic recording (HAMR) magnetically records data on high-stability media (such as iron platinum alloy) using laser thermal assistance to first heat the material, which allows to greatly reduce the size of “pitches” without negative effects on read-ability, write-ability and stability. As a result, HDDs featuring HAMR will be able to store considerably higher amounts of data than today’s hard drives featuring perpendicular recording tech.Source: Kitguru
Previously it was believed that HAMR will only become viable sometimes in 2017, but in the recent years TDK, Seagate and Western Digital intensified their HAMR development and even demonstrated working HDDs featuring the technology.