Perspectives of Read Head Technology for 10 Tb/in $^{2}$ Recording

For a read head design, two of the most important parameters are the resolution and the signal to the noise ratio (SNR). For 10 Tb/in² recording, the sensor dimensions required to achieve the resolutions are derived for various bit aspect ratio (BAR) designs. It is shown that the today´s shielded read head technology is unable to scale down to meet the linear density requirement. By analyzing the data rate requirements at various BAR values, it is argued that the current tunnel magnetoresistance head is no longer suitable to provide high SNR due to its high impedance. A differential dual spin valve (DDSV) , which does not need to have magnetic shields, is proposed to achieve the required SNR and linear resolution of the read head for 10 Tb/in². A systematical analysis on the effect of stiffness field, magnetic shields and media field shows that thermally activated magnetic noise may not necessarily be a crucial limiting factor for 10 Tb/in². The conventional course to increase SNR by increasing GMR ratio is still applicable. Assuming realistic constraints and requirements, we come out with the DDSV reader specifications for 10 Tb/in² recording. With a stiffness field of 300 Oe and an operating current density of 4 ? 10⁷ A/cm², a SNR of 20 dB can be achieved under a media field of 300 Oe for an unshielded DDSV reader having a GMR ratio of 12%. Preliminary studies show that DDSV is very promising for the application in 10 Tb/in². The differential effect in DDSV is demonstrated using two types of dual spin valve. For a dual spin valve with two reference layer (RL) magnetizations in the same direction, the total resistance change under uniform field is the sum of two spin valves as expected, while for another similar dual spin valve but with the two RL magnetizations in the opposite direction, no resistance change is observed in the dynamic field region from 300 Oe to - 300 Oe.