R&D: Three Articles on HAMR Technologies and Solutions

R&D: Influence of thermal gradient and cooling rate on writability in heat-assisted magnetic recording
Authors analyze the influence of thermal gradient and cooling rate on writability in 4 Tbpsi shingled heat-assisted magnetic recording employing a stochastic calculation.

Journal of the Magnetics Society of Japan has published an article written by T. Kobayashi, Graduate School of Engineering, Mie Univ., 1577 Kurimamachiya-cho, Tsu 514-8507, Japan, Y. Nakatani, Graduate School of Informatics and Engineering, Univ. of Electro-Communications, 1-5-1 Chofugaoka, Chofu 182-8585, Japan, and I. Tagawa, Electrical and Electronic Engineering, Tohoku Institute of Technology, 35-1 Yagiyama-Kasumicho, Sendai 982-8577, Japan.

Abstract: “We analyze the influence of thermal gradient and cooling rate on writability in 4 Tbpsi shingled heat-assisted magnetic recording employing a stochastic calculation. We separate the bit error rate bER for each grain column in 2 bits of data and focus on the mean magnetization reversal number per unit time 𝑁_– for the medium in the recording direction during writing. We introduce the medium writing temperature 𝛥𝑇_med and time 𝜏_med, which are temperature and time ranges, respectively, where the 𝑁_– value is larger than 1 ns^-1. We also introduce the Curie temperature variation time 𝜏_Tc and the field end temperature 𝑇_end. The 𝜏_med and 𝜏_Tc values are functions of the cooling rate, which is the product of the thermal gradient and the linear velocity. In contrast, the 𝑇_end value is a function of the thermal gradient only. When the writing field is small, write-error and erasure-before-write are mainly dominant, and the bER value is determined by the 𝜏_med and 𝜏_Tc values, respectively. When the writing field is large, erasure-after-write is mainly dominant, and the bER value is determined by the 𝑇_end value in addition to the 𝜏_Tc value.“

R&D: Rapid heat-assisted polarization reversal in a ferroelectric thin film
Authors demonstrate that switching of ferroelectric thin films sandwiched between metallic electrodes can be controlled by laser-assisted heating, reminiscent of HAMR.

Applied Physics Letters has published an article written by Rekikua Alemayehu, Steffen Zeuschner, Alexander von Reppert, Institut für Physik und Astronomie, Universität Potsdam, 14476 Potsdam, Germany, Matthias Rössle, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Wilhelm-Conrad-Röntgen Campus, BESSY II, 12489 Berlin, Germany, Marin Alexe, Institute of Physics, Warwick University, Coventry, United Kingdom, and Matias Bargheer, Institut für Physik und Astronomie, Universität Potsdam, 14476 Potsdam, Germany, and Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Wilhelm-Conrad-Röntgen Campus, BESSY II, 12489 Berlin, Germany.

Abstract: “We demonstrate that switching of ferroelectric thin films sandwiched between metallic electrodes can be controlled by laser-assisted heating, reminiscent of heat-assisted magnetic recording. We employ electrical switching cycles that quantify the electrically switchable remanent polarization Pr and show that 300 ns voltage pulses alone change the polarization by less than ΔP<Pr⁠. Transient heating of the metallic top electrode by synchronized ns laser pulses induces a reversal ΔPL>Pr of the average polarization. The transient average temperature modeled by the heat equation can rationalize the polarization change observed for different relative timings Δt of the laser pulse if it arrives before the electrical pulse.“

R&D: Tunable positive and negative exchange bias in TmCrO₃ thin films grown for heat-assisted magnetic recording
TmCrO₃ thin films offer a solution through their hallmark property-a temperature tunable positive and negative exchange bias-making them promising functional materials for HAMR read-write heads.

Journal of Alloys and Compounds has published an article written by Xin Zhang, Guangxi Key Laboratory of Information Materials, Guilin University of Electronic Technology, Guilin 541004, PR China, and School of Materials Science and Engineering, Guilin University of Electronic Technology, Guilin 541004, PR China, Dianhai Su, School of Materials Science and Engineering, Guilin University of Electronic Technology, Guilin 541004, PR China, Songwei Wang, Key Laboratory of Information Materials, Guilin University of Electronic Technology, Guilin 541004, PR China, and School of Materials Science and Engineering, Guilin University of Electronic Technology, Guilin 541004, PR China, Shizheng Tian, Shiwen Hong, School of Materials Science and Engineering, Guilin University of Electronic Technology, Guilin 541004, PR China, Laijun Liu, College of Materials Science and Engineering, Guilin University of Technology, Guilin 541004, PR China, Jingtai Zhao, and Guanghui Rao, Guangxi Key Laboratory of Information Materials, Guilin University of Electronic Technology, Guilin 541004, PR China, and School of Materials Science and Engineering, Guilin University of Electronic Technology, Guilin 541004, PR China.

Abstract: “Heat-Assisted Magnetic Recording (HAMR), the leading technology for ultra-high-density storage, faces a critical challenge in synchronizing thermal and magnetic control. TmCrO₃ thin films offer a solution through their hallmark property-a temperature tunable positive and negative exchange bias-making them promising functional materials for HAMR read-write heads. Herein, high-quality TmCrO₃ films were grown via pulsed laser deposition on SrTiO₃ (001). Magnetic characterization shows a reduced compensation temperature (20 K vs. 26 K in bulk) due to strain-induced lattice mismatch. The film exhibits significant magnetic anisotropy and exchange bias, with sign reversal near compensation temperature caused by antiferromagnetic coupling between Tm- and Cr-sublattices. The out-of-plane exchange bias is stronger due to compressive strain aligning perpendicularly to the antiferromagnetic easy axis, enhancing pinning. An exchange bias model for TmCrO₃ systems was developed, offering new insights into sign reversal in single-phase compounds.“