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 Fe x Al1–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.

Magnetic and Magnetocaloric Modifications near Room Temperature in Fe0.6Al0.4 Nanoalloys under Irradiation by Swift Heavy Ions

“…In recent decades, there has been significant interest in the understanding of magnetic and magnetocaloric properties of alloys and compounds upon the basis of transition metals like Fe or Co. − Currently, magnetic refrigeration is widely acknowledged to be an energy-efficient and environmentally friendly commercialized technology. In these studies, there is room for magnetic nanostructured materials, whose properties can differ from those in their bulk counterparts. − Many of these features, intrinsic for magnetic nanomaterials, have great potential for their use in data storage, biomedical, environmental, and heterogeneous catalysis applications. For implications of magnetic nanostructures in magnetocalorics, the absence of magnetic hysteresis and zero remnant magnetization would be a necessary condition. − This is achievable in the systems containing noninteracting magnetic/magnetizable nanoparticles or superparamagnetic (SPM) clusters, for which the magnetic behavior is nonhysteretic.…”

“…Due to interfacial exchange with strong ferromagnets, a weakly FM matrix (PM with low but nonzero T C ) is magnetized, thus decreasing its magnetic entropy. In the present work, we investigate this concept using thin film (50 nm)-shaped samples of Fe 0.6 Al 0.4 alloys that exhibit thermally induced phase transformations from the FM to PM-like state (with no hysteresis and remanence) at RT. ,− ,− In the literature cited above, there is a consensus that this transition is caused by chemical ordering in the atomic lattice, from the initially disordered state A2 with high T C to the ordered B2 state with low T C , as schematically illustrated in Figure a. Under irradiation with swift heavy ions, a reverse transformation, from the B2 to A2 state, can be expected.…”

Template-based electrodeposited nonmagnetic and magnetic metal nanowire arrays as building blocks of future nanoscale applications

“…The creation of miniature nanodevices used in future advanced technological applications such as magnetic information storage [1,2], energy storage and conversion [3,4], electronics [5], biosensing [6], microwave absorption [7,8] and magnetoresistive memories [9,10], involves size-and compositioncontrolled materials at the nanoscale with tunable properties. In fact, small changes in size and composition can considerably impact nanomaterials in terms of structural, crystalline, chemical, optical, electrical and magnetic properties, among others.…”