A prototype TMR head
A prototype TMR head
[Click to enlarge image]

TDK Corp achieved the world's highest surface recording density of HDD, 803Gbit/inch2, with a track recording density of 1,771kBPI, a track density of 454kTPI and a track pitch of 56nm.

In terms of a single 1.8-inch double-sided disk, it amounts to about 260-Gbyte capacity.

The composition of the head and medium is the same as announced in 2007: a TMR head with a MgO insulating film and a discrete track medium. TDK developed the medium based on a perpendicular magnetic recording HDD of Showa Denko K K.

To enhance the surface recording density, TDK increased the magnetoresistance ratio by more than 80% while keeping the bond resistance of the reproducing head's TMR element low.

"We got a feeling that we will be able to achieve up to 1Tbit/inch2 with TMR elements," said Katsumichi Tagami, director of the SQ Research Center, TDK Technology Group.

In general, when a TMR element is downsized in accordance with an increase in track density, the resistance of the element increases, making it difficult to read out at high speeds. Therefore, it has been expected that CPP-GMR elements, whose resistance is lower than that of TMR elements, will replace TMR elements before surface recording density reaches 1Tbit/inch2.