Research groups from NIMS, Sea­gate Tech­nol­o­gy, and Tohoku Uni­ver­si­ty have made a break­through in the field of hard disk dri­ves (HDD) by demon­strat­ing the fea­si­bil­i­ty of mul­ti-lev­el record­ing using a three-dimen­sion­al mag­net­ic record­ing medi­um to store dig­i­tal infor­ma­tion.

The research groups have shown that this tech­nol­o­gy can be used to increase the stor­age capac­i­ty of HDDs, which could lead to more effi­cient and cost-effec­tive data stor­age solu­tions in the future.

Data cen­ters are increas­ing­ly stor­ing vast amounts of data on hard disk dri­ves (HDDs) that use per­pen­dic­u­lar mag­net­ic record­ing (PMR) to store infor­ma­tion at are­al den­si­ties of about 1.5 Tbit/in². How­ev­er, to tran­si­tion to high­er are­al den­si­ties, a high anisotropy mag­net­ic record­ing medi­um con­sist­ing of FePt grains com­bined with heat-assist­ed laser writ­ing is required.

This method, known as heat-assist­ed mag­net­ic record­ing (HAMR), is capa­ble of sus­tain­ing are­al record­ing den­si­ties of up to 10 Tbit/in². Fur­ther­more, den­si­ties of larg­er than 10 Tbit/in² are pos­si­ble based on a new prin­ci­ple demon­strat­ed by stor­ing mul­ti­ple record­ing lev­els of 3 or 4 com­pared with the bina­ry lev­el used in HDD tech­nol­o­gy.

In the study, pub­lished in Acta Mate­ri­ala, the team suc­ceed­ed in arrang­ing the FePt record­ing lay­ers three dimen­sion­al­ly, by fab­ri­cat­ing lat­tice-matched, FePt/Ru/FePt mul­ti­lay­er films, with Ru as a spac­er lay­er.

Mea­sure­ments of the mag­ne­ti­za­tion show the two FePt lay­ers have dif­fer­ent Curie tem­per­a­tures. This means that three-dimen­sion­al record­ing becomes pos­si­ble by adjust­ing the laser pow­er when writ­ing.

In addi­tion, the researchers demon­strat­ed the prin­ci­ple of 3D record­ing through record­ing sim­u­la­tions, using a media mod­el that mim­ics the microstruc­ture and mag­net­ic prop­er­ties of the fab­ri­cat­ed media.

The three-dimen­sion­al mag­net­ic record­ing method can increase record­ing capac­i­ty by stack­ing record­ing lay­ers in three dimen­sions. This means that more dig­i­tal infor­ma­tion can be stored with few­er HDDs, lead­ing to ener­gy sav­ings for data cen­ters.

In the future, the researchers plan to devel­op process­es to reduce the size of FePt grains, to improve the ori­en­ta­tion and mag­net­ic anisotropy, and to stack more FePt lay­ers to real­ize a media struc­ture suit­able for prac­ti­cal use as a high-den­si­ty HDD.