Simulation of Chemical Order–Disorder Transitions Induced Thermally at the Nanoscale for Magnetic Recording and Data Storage

Abstract

In memory nanodevices based on phase changes induced thermally, the process of information recording is a reversible transition between the structurally ordered (crystalline) and disordered (amorphous) phases that can provide a difference in the physical properties of these two states, for example, in optical reflectivity, electrical resistivity, or magnetic permeability. It is of particular interest to explore whether the chemical disorder is erasable, rewritable, and scalable in solid alloys upon their exposure to short heating pulses. Here, we model this process by assuming second-order phase transitions between chemically ordered and disordered states in the atomic lattice. Our simulations reveal that nanosecond laser irradiation concentrated within a nanoscale spot on the sample surface is able to induce reversible chemical-order (B2)-disorder (A2) transformations (CODTs) in intermetallic Fe-rich FexAl1–x alloys that exhibit the disorder-induced ferromagnetism. A realization of this concept would provide an alternative approach to current technologies for magnetic recording and data storage, in which the written bits are represented by regions with not a different polarity but with a different magnitude of magnetization. We envision that the proposed approach can be realized with tools used currently for heat-assisted magnetic recording (HAMR), for example, with a near-field transducer (NFT). A specific design for CODT-based magnetic recording media is proposed.