C-doping Anisotropy Effects on Borophene Electronic Transport

The electronic transport anisotropy for different C-doped borophene polymorphs (β12 and χ3) was investigated theoretically combining density functional theory (DFT) and non-equilibrium Green’s function (NEGF). The energetic stability analysis reveals that B atoms replaced by C is more energetically favorable for χ3 phase. We also verify a directional character of the electronic band structure on C-doped borophene for both phases. Simulated Scanning tunneling microscopy (STM) and also total density of charge confirm the directional character of the bonds. The zero bias transmission for β12 phase at E − EF = 0 shows that C-doping induces a local current confinement along the lines of doped sites. The I − V curves show that C-doping leads to an anisotropy amplification in the β12 than in the χ3. The possibility of confining the electronic current at an specific region of the C-doped systems, along with the different adsorption features of the doped sites, poses them as promising candidates to highly sensitive and selective gas sensors.

Effects of carbon doping on structure and magnetocaloric properties of Mn1.25Fe0.7P0.5Si0.5 alloys

(Mn,Fe)2(P,Si)-basedmaterials are promisingly applied in the room-temperature magnetic refrigeration field. In this study, Mn1.25Fe0.7P0.5Si0.5Cx (x = 0, 0.01, 0.03 and 0.05) alloys were prepared by arc-melting and then a two-stage sintering process. The effects of C doping on the crystal structure and magnetocaloric behavior are discussed. Results indicate that the Fe2P-type structure (space group of P62 m) was crystallized for all samples with weakened first-order magnetic transitions (FOMT). The Curie temperature could be altered from 223.5 K to 278.5 K with the large magnetocaloric effect (MCE) remaining by C doping. In the applied magnetic field of 5 T, the peak value of magnetic entropy change (–ΔS M) increased by 7.3% to reach 25.1 J × kg–1 × K–1. The temperature-induced entropy change (ΔS DSC) derived from DSC was slightly larger than ΔS M induced by the magnetic field. The Mn1.25Fe0.7P0.5Si0.5 alloys with large MCE can be effectively tuned by C doping because C atoms prefered to share the substitute and occupy the interstitial sites in hexagonal Fe2P-type structure.

Stabilization of ferromagnetism in carbon doped Mgn−2Mn2On clusters

We present density functional theory-based first principles study of magnetic properties of Mn-doped Mg[Formula: see text]Mn2On clusters. Mn-doped MgnOn clusters are found to exhibit antiferromagnetic order. We show that ferromagnetic state can be stabilized by codoping with carbon at oxygen site. Our study suggests that the holes created due to C doping are responsible for the stabilization of ferromagnetism.

Effects of Carbon Doping and Annealing Temperature on Magnetic MnAl Powders and MnAl Polymeric Composites

Process parameters leading to magnetic polymer composites, an essential ingredient in the additive manufacturing of rare-earth-free magnets, are investigated. The induction melting of manganese (Mn) and aluminum (Al), and subsequent annealing at 450, 500, or 550 °C for 20 min, gave rise to ferromagnetic τ–MnAl phase, as well as other phases. The nonmagnetic Al4C3 and oxide phases were then removed by the magnetic separation. Magnetic powders from the magnetic separation were incorporated in polylactic acid (PLA) matrix via a solution route. The remanent magnetization as high as 4.3 emu/g in the powder form was reduced to 2.3–2.6 emu/g in the composites. The reduction in coercivity was minimal, and the largest value of 814 Oe was obtained when the powder annealed at 450 °C was loaded in the composite. The phase composition and hence magnetic properties were even more sensitive to the carbon (C) doping. Interestingly, the addition of 3% C led to coercivity as high as 1445 Oe in MnAl–C powders without further annealing. The enhanced coercivity was attributed to the domain wall pinning by the AlMn3C phase, and magnetizations are likely increased by this phase.