Modulating Multiferroic Control of Magnetocrystalline Anisotropy Using 5d Transition Metal Capping Layers

Intrinsic ferromagnetism in two-dimensional 1T-MX2 monolayers with tunable magnetocrystalline anisotropy

Two-dimensional (2D) ferromagnetic materials with tunable magnetocrystalline anisotropy (MCA) provide unique opportunities for developing the next-generation data-storage and information devices. Herein we systematically investigate the electronic and magnetic properties of the 1T-MX2 (M = Cr, Mn, Fe, Co; X = As, Sb) monolayers, and identify the stable 2D ferromagnets as well as their MCA energies. Notably, the results demonstrate that the biaxial strain and carrier doping effects have a significant influence on their magnetic behaviors. In addition to the robust FM states, three FM monolayers yield tunable MCA depending on the applied strain type and carrier doping values. The dominant contributions to these complicated modifications in MCA are mainly attributed to the strain or carrier doping induced alterations of specific M-derived 3d states, which in turn lead to the changes of their spin-orbit coupling (SOC) energies. These findings show effective approaches to control 2D magnetism and suggest that these 2D FM materials may be promising candidates to design highly efficient memory devices.

Tunable magnetocrystalline anisotropy of two-dimensional Fe3GeTe2 with adsorbed 5d-transition metal

The demand for ultra-compact spintronic devices with lower energy consumption and higher storage density requires two-dimensional (2D) magnetic materials with tunable magnetocrystalline anisotropy (MCA) energy. Employing first-principles calculations, we have investigated the influence of W atom adsorption and biaxial strain on the magnetic properties of layered Fe₃GeTe₂. We demonstrate that the adsorption mode and applied strain play a critical role in determining their MCA. The Fe₃GeTe₂ adsorbed with W atoms undergoes a change in spin reorientation from out-of-plane to in-plane magnetization, yielding a colossal MCA up to -13.112 erg cm^-2. The dominant contribution to these unexpected changes mainly arises from the W atoms with emerged magnetism and large SOC. Moreover, our results reveal distinct strain-driven modulation behaviors of the MCA in different adsorption configurations. The underlying atomistic mechanism mainly involves the alteration of various W-derived 5d-orbital states under the strain effect, leading to competitive changes of the corresponding spin-orbit coupling energies between the spin-parallel and spin-flip channels. Our findings not only provide useful guidance in optimizing the MCA performance of 2D magnetic crystals but also highlight the potential of W-adsorbed Fe₃GeTe₂ in the applications of new-generation magnetic memory storage devices.

Self-assembled magnetic heterostructure of Co/DLC films

In order to adapt to the quick and large amount of necessity in data flow for 5G cloud generation, it is necessary to develop a technology of warm storage device in market which takes a great balance between the reading/writing performance and the price per storage capacity. The technologies of warm storage devices are assumed to adopt phase change memory (PCM), resistive random access memory or magnetoresistive random access memory which have the highest possibilities to 5G structures and magnetic properties of Co on non-hydrogenated diamond like carbon (DLC)/Si(100) films and Co/DLC interface are investigated. The self-assembled magnetic heterostructure is firstly reported in hexagonal close packing Co layers perpendicular magnetic anisotropy (PMA) on Co carbide layers (in-plane) during Co deposited on DLC/Si(100). A PMA/in-plane magnetic heterostructure is expected to have the highest switching current to the energy barrier ratio of near 4 in previous report, which has great potential for developing warm memory devices. Based on these unique characteristics, we provide a novel design called magnetic anisotropy-phase change memory (Mani-PCM) which can impact the developing blueprint of memory. The working process of Mani-PCM includes in set, reset and read states as a universal PCM. This brand new technology is highly promising as warm memory devices including high reading/writing performance and economical price per storage capacity.

Thickness and Ferroelectric Polarization Influence on Film Magnetic Anisotropy across a Multiferroic Material Interface

The ferroelectric switching effect on perpendicular magnetic anisotropy is examined for the case of the BaTiO₃/L1₀-CoFe interface through first-principles calculations of film magnetocrystalline anisotropy energy (MAE), both with the frozen-potential method and the second-order perturbation theory. The ferroelectric switching-MAE relationship is shown to have opposite trends for BaO- and TiO₂-terminated interfaces because of the distinct orbital interaction mechanisms predominant in each termination configuration. The ferroelectric switching effect, changes in Fe-O bond lengths, and termination constitute three different contributors to MAE change, each with a different penetration depth into the CoFe film. The top surface CoFe atoms are shown to feature a high density of minority-spin 3d_xz states, which could play a role in influencing the ferroelectric switching-MAE relationship in cases where the top surface undergoes modifications.