Search

In this article, we present a novel micromagnetic model for L10 ordered FePt grains based on their atomic structure. In this model, each monolayer of Fe atoms is represented by a magnetic moment vector and the entire grain consists of a stack of magnetic moments coupled by magnetostatic and nearest-neighbor exchange fields. The grain model enables simulation of incoherent magnetization switching, especially near the Curie temperature. The model is applied to simulate the heat-assisted recording process in granular L10 FePt thin-film media. One of the unique findings is that grains at transition centers could have a domain wall trapped within, provided sufficient grain height. The existence of these grains, whose magnetic moments could be fractional at transition centers, resulting in significant reduction of medium noise. The noise reduction is effectively equivalent to an increase of the number of grains across the read track width. Enhancing and controlling this mechanism by material engineering could lead to significant increase of area density capability, specifically, increase of track density, without decreasing grain size. [ABSTRACT FROM AUTHOR]

The Curie temperature distribution induced from grain size variation in heat-assisted magnetic recording (HAMR) can be alleviated by including the thermally insulating magnetic grain boundaries. In this paper, we present a systematic micromagnetic study on this new type of HAMR media, focusing on the impact to the recording behaviors from the exchange coupled magnetic boundary (shell). It is found that the soft magnetic shell of higher Curie temperature is capable of assisting the switching of FePt grain in both magnetization and transition process. The important implication of the proposed media for practical HAMR recording is that optimal performance now can be accomplished with relaxed recording conditions in both head field intensity and the heating source, eventually enhancing area density capability and the overall HAMR system stability. [ABSTRACT FROM AUTHOR]

Transition curvature in heat-assisted magnetic recording can be eliminated by appropriately varying head field amplitude across recording track width. In this paper, we present a systematic micromagnetic study on the effects of non-vanishing field beyond track edges in practical head designs, focusing on the recording characteristics beyond track edges. It is found that a uniform field amplitude beyond track edges will create wing-like patterns beyond straightened transitions, forming erase bands at high linear densities. The width of the erase band decreases if the head field diminishes beyond track edges. However, for practical field reduction gradients beyond track edges, the width of the erase band still remains significant. [ABSTRACT FROM AUTHOR]

Resulting from the curved thermal profile by near-field transducers, the transition curvature in heat-assisted magnetic recording is one of the critical factors significantly limiting the technology from achieving expected high area density capability. In this paper, we present a systematic micromagnetic modeling study to understand the underlying physics and to arrive at a solution that can correct the transition curvature for enhancing recording performance. Analysis show that the straightened transitions of the recording with the solution can yield a linear density increase of 50% at the same high track densities. [ABSTRACT FROM AUTHOR]

In this paper, we report a micromagnetic modeling study on the recording processes in heat-assisted magnetic recording. By solving coupled Landau-Lifshitz-Bloch equations, recording simulations are performed for granular \FePt-L10 thin film media. The calculated signal-to-noise ratio shows strong dependence on recording field amplitude, especially for media of small size grains. It is found that low field amplitude yields unsaturated recording whereas high field amplitude causes transitions to be broadened immediately after writing. High thermal gradient will alleviate the transition broadening, allowing high field amplitude to be employed so that completed magnetization in the recorded bits can be achieved in small grin size media. The study concludes that the ability in obtaining the expected signal-to-noise ratio performance at very small grain pitches would critically rely on whether sufficiently high thermal gradient can be achieved in the media. [ABSTRACT FROM AUTHOR]

Heat-assisted magnetic recording utilizes material with drastically changing crystalline anisotropy during the heating and cooling process. In this paper, the impact of media anisotropy near Curie temperature on medium signal-to-noise ratio (SNR) is systematically studied. Results show that the combination of proper gradient of anisotropy versus temperature and thermal profile is crucial to achieving satisfactory SNR and recording areal density. [ABSTRACT FROM AUTHOR]

Abstract: A method of heat-assisted magnetic recording (HAMR) potentially suitable for probe-based storage systems is characterized. In this work, field emission current from a scanning tunneling microscope (STM) tip is used as the heating source. Pulse voltages of 2–7V were applied to a CoNi/Pt multilayered film fabricated on either bare silicon or oxidized silicon substrates. Different types of Ir/Pt and W STM tips were used in the experiment. The results show that thermally recorded magnetic marks are formed with a nearly uniform mark size of 170nm on the film fabricated on bare silicon substrate when the pulse voltage is above a threshold voltage. The mark size becomes 260nm when they are written on the identical film fabricated on an oxidized silicon substrate. The threshold voltage depends on the material work function of the tip, with W having a threshold voltage about 1V lower than Pt. A synthesized model, which contains the calculation of the emission current, the simulation of heat transfer during heating, and the study of magnetic domain formation, was introduced to explain experimental results. The simulation agrees well with the experiments. [Copyright &y& Elsevier]