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

Abstract

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.

Impact of lattice dynamics on the phase stability of metamagnetic FeRh: Bulk and thin films

“…The advantage is that the first-order phase transition of FeRh can be tailored well below the Curie temperature of FePt, which relaxes the lifetime and reliability problem of the NFCs. Furthermore, during recording, the magnetic moment of FeRh is still high overcoming the problem of thermally written-in errors [14]. Another exciting application of FeRh is in the developing field of spintronics, which is promising significant advantages in data storage [15].…”

Superior bit error rate and jitter due to improved switching field distribution in exchange spring magnetic recording media

“… 29 . It has to be noted that in heat assisted recording besides the transition jitter which leads to AC noise also thermally written in errors are a serious problem that lead to DC error 1 29 . Whereas the jitter decreases in heat assisted recording if the write temperature is increased, with higher temperature DC noise increase, DC noise is expected to be a much smaller problem in non-heat assisted recording since the temperature is much smaller during writing and a higher Zeeman energy during writing helps to reverse the grain in the correct state.…”

“…In addition, intrinsic noise due to the thermal fluctuations during writing has to be minimized. This is a particular challenge in heat-assisted recording, where the write process occurs at elevated temperature 1 2 . In heat-assisted recording for smaller grain sizes, both (i) the fundamental jitter due to thermal fluctuations during writing as well as (ii) the T c distributions are expected to increase.…”

Computational micromagnetics with Commics

“…Typical micromagnetic models exhibit length scales ranging from nanometers to few micrometers, which is often infeasible for atomistic spin dynamics simulations. In recent decades, micromagnetics evolved as a computational field, that nowadays represents a successful tool for numerical studies in materials science with important contemporary applications, e.g., data storage structures like hard disk drives [76,54], random access memories [61], or nanowires [73,50], magnetologic devices [24], soft magnetic sensor systems [34], and high performance permanent magnets [72,23,43].…”