ИСТИНА

Heat assisted magnetic recording (HAMR) is a new technology which uses temporary near field heating of the media during write to increase hard disk drive storage density. By using a plasmonic antenna embedded in the write head, an extremely high thermal gradient is created in the recording media (up to 10K/nm). State of the art HAMR media consists of grains of L1 0-FePt exhibiting high perpendicular anisotropy separated by 1 to 2 nm thick carbon segregant. Next to the plasmonic antenna, the difference of temperature between two nanosized FePt grains in the media can reach 80K across the 2 nm thick grain boundary. This represents a gigantic local thermal gradient of 40K/nm across a carbon tunnel barrier. In the field of spincaloritronics, much weaker thermal gradients of ~1K/nm were shown to cause a thermal spin-transfer torque capable of inducing magnetization switching in magnetic tunnel junctions. Considering that the thermal gradients in HAMR are one to two orders of magnitude larger than those used in conventional spincaloritronic experiments, one may expect a strong impact from these thermal spin-transfer torques on magnetization switching dynamics in HAMR recording. This study addresses this problem. It combines theory, experiments aiming at determining the polarization of tunneling electrons across the media grain boundaries and micromagnetic simulations of recording process taking into account these thermal gradients. It is shown that the thermal in-plane torque can have a detrimental impact on the recording performances by favoring antiparallel magnetic alignment between neigh - boring grains during the media cooling. Implications on media design are discussed in order to overcome the influence of these thermal torques. Suggestions of spincaloritronic experiments taking advantage of these huge thermal gradients produced by plasmonic antenna will also be given.