Approaching the Grain-Size Limit for Jitter Using FeRh/FePt in Heat-Assisted Magnetic Recording

Huang, Pin Wei; Victora, R. H.

doi:10.1109/tmag.2014.2318040

Cited by 18 publications

(7 citation statements)

References 17 publications

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“…In contrast to the Curie temperature, which is a second-order phase transition and per definition does not show an infinite fast change of the magnetization as a function of temperature, first-order phase transitions show a jump at the critical temperature. 20,21 In Ref. 22, the transition temperature of a 50-nm-thick FeRh film was investigated, where the transition from non-magnetic to magnetic occurs at a temperature of T ¼ $345 K, with a standard deviation of approximately 3-4 K. In Ref.…”

Section: Discussionmentioning

confidence: 99%

Fundamental limits in heat-assisted magnetic recording and methods to overcome it with exchange spring structures

Suess

Vogler

Abert

et al. 2015

Journal of Applied Physics

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The switching probability of magnetic elements for heat assisted recording is investigated. It is found that FePt elements with a diameter of 5 nm and a height of 10nm show, at a field of 0.5 T, thermally written in errors of 12%, which is significant too large for bit patterned magnetic recording. Thermally written in errors can be decreased if larger head fields are applied. However, larger fields lead to an increase the fundamental thermal jitter. This leads to a dilemma between thermally written in errors and fundamental thermal jitter. This dilemma can be partly relaxed by increasing the thickness of the FePt film up to 30nm. For realistic head fields, it is found that the fundamental thermal jitter is in the same order of magnitude of the fundamental thermal jitter in conventional recording, which is about 0.5 -0.8 nm. Composite structures consisting of high Curie top layer and FePt as hard magnetic storage layer can reduce the thermally written in errors to be smaller than 10 -4 if the damping constant is increased in the soft layer. Large damping may be realized by doping with rare earth elements. Similar to single FePt grains also in composite structure an increase of switching probability is sacrifices by an increase of thermal jitter. Structures utilizing first order phase transitions breaking the thermal jitter and writeability dilemma are discussed.

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Section: Discussionmentioning

confidence: 99%

Fundamental limits in heat-assisted magnetic recording and methods to overcome it with exchange spring structures

Suess

Vogler

Abert

et al. 2015

Journal of Applied Physics

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“…However, even if perfect L1 0 -FePt particles down to 3 nm in diameter with unity order parameter can be fabricated, recent theoretical predictions [9] and simulations show that thermally induced errors due to the large thermal energy of grains under recording during HAMR processes will start to cancel the benefits from using smaller grains (<5 nm) or even worsen the performance, as shown in [5] and [10] via transition jitter and medium SNR calculations, respectively. In our recent work [11], we mentioned that, in recording with granular media, exchange-coupled composite grains would be ultimately advantageous only when using FeRh as a soft assisting layer. Through micromagnetic recording simulation we have shown in [11] that recording at the grain size limit with 6.6 nm average GP (1 nm grain boundaries) can be achieved by using grains with FeRh/FePt composite structures.…”

Section: B Medium Design With Iron-rhodium and Chromiummentioning

confidence: 99%

“…In our recent work [11], we mentioned that, in recording with granular media, exchange-coupled composite grains would be ultimately advantageous only when using FeRh as a soft assisting layer. Through micromagnetic recording simulation we have shown in [11] that recording at the grain size limit with 6.6 nm average GP (1 nm grain boundaries) can be achieved by using grains with FeRh/FePt composite structures.…”

Section: B Medium Design With Iron-rhodium and Chromiummentioning

confidence: 99%

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Noise Mitigation in Granular and Bit-Patterned Media for HAMR

et al. 2015

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Feasibility of heat assisted magnetic recording for granular and bit-patterned media (BPM) is evaluated in the context of various noises. Using micromagnetic simulation of renormalized media cells, we predict that the jitter is only 0.58 nm at a head speed of 10 m/s for the bilayer structure of FeRh/FePt when the grain size is 3.2 nm, validating the possibility of 6 Tb/in 2 . We propose a new structure FePt/Cr/X/FePt that uses a Cr layer to produce an antiferromagnetic coupling that mimics the behavior of FeRh/FePt. We also confirmed the consistency of our renormalization approach for cell sizes from 1.0 to 1.5 nm. The temperature distribution is analyzed for BPM for areal densities of 2.2-5 Tb/in 2 . We have predicted the maximum tolerable on-track bit temperatures at different areal densities and filling factors and substantiate the feasibility of BPM at 5 Tb/in 2 by observing successful and deterministic switching under a realistic temperature distribution.Index Terms-Bit-patterned media (BPM), FePt, granular media, heat assisted magnetic recording (HAMR), noise.

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“…Media with capped layers can address this problem, as the exchange coupling added by layers (such as FePt, FeRh, or Fe, proposed by others) can compensate the magnetostatic interaction. 16,[18][19][20][21][22][23][24][25][26] However, these materials become ineffective in the case of HAMR, as materials such as FePt and Fe lose ferromagnetism at high temperature during recording. As a result, the high temperature SFD is still higher in HAMR media.…”

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confidence: 99%

Exchange coupled CoPt/FePtC media for heat assisted magnetic recording

Dutta

Piramanayagam

et al. 2018

Applied Physics Letters

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L10 FePtC granular media are being studied as potential future magnetic recording media and are set to be used in conjunction with heat assisted magnetic recording (HAMR) to enable recording at write fields within the range of current day recording heads. Media structures based on a FePtC storage layer and a capping layer can alleviate the switching field distribution (SFD) requirements of HAMR and reduce the noise originating from the writing process. However, the current designs suffer from SFD issues due to high temperature writing. To overcome this problem, we study a CoPt/FePtC exchange coupled composite structure, where FePtC serves as the storage layer and CoPt (with higher Curie temperature, Tc) as the capping layer. CoPt remains ferromagnetic at near Tc of FePtC. Consequently, the counter exchange energy from CoPt would reduce the noise resulting from the adjacent grain interactions during the writing process. CoPt/FePtC bilayer samples with different thicknesses of CoPt were investigated. Our studies found that CoPt forms a continuous layer at a thickness of 6 nm and leads to considerable reduction in the saturation field and its distribution.

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Approaching the Grain-Size Limit for Jitter Using FeRh/FePt in Heat-Assisted Magnetic Recording

Cited by 18 publications

References 17 publications

Fundamental limits in heat-assisted magnetic recording and methods to overcome it with exchange spring structures

Fundamental limits in heat-assisted magnetic recording and methods to overcome it with exchange spring structures

Noise Mitigation in Granular and Bit-Patterned Media for HAMR

Exchange coupled CoPt/FePtC media for heat assisted magnetic recording

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