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An active attitude control system using a novel six-layer electromagnetic embedded printed magnetorquer for a 3-U nanosatellite is presented in this paper. The proposed design was optimized in terms of size, dissipated power, torque produced, and generated magnetic dipole moment. The designed printed magnetorquer is the optimum choice for a 3-U small-satellite attitude stabilization in terms of reconfigurability, modularity, lower space occupation, low mass, and lower cost. The printed magnetorquer was designed and analyzed for a 3-U nanosatellite with CubeSat standard dimensions of 10×10×30 cm3. The design was implemented with commercial off-the-shelf (COTS) high-performance microdevices that are reliable and easily accessible for reducing procurement cost. The printed magnetorquer was embedded in internal layers of a printed circuit board (PCB) that does not require additional space on the satellite. Time-varying rotational analyses were performed for various coil arrangements to test the rotation times for spin-stabilized 3-U nanosatellites. Thermal analysis of the 3-U nanosatellite was done to sustain thermal operation and satisfy the feasibility requirements of the system. Essential performance parameters like magnetic moment generated, resultant torque, and power dissipation were examined for comparison with the existing commercial state of the art. The proposed printed magnetorquer with more configurability (2×3 , 3×2 , 1×18 , 18×1 , 9×2 , 6×3 hybrid) features provides versatility to the design aspects by changing the configuration through the onboard computer according to mission needs. [ABSTRACT FROM AUTHOR]

The effects of various vacancies and group‐VIB and VIIB transition metal substitutional doping on the structural, electronic, and magnetic properties of monolayer HfS2 are studied by first‐principles calculations. The results show that pristine monolayer HfS2 is a nonmagnetic semiconductor; it becomes a metal on creating a single V1Hf or V1S vacancy, whereas it is still a semiconductor on creating V1Hf+1S divacancy or V1Hf+2S trivacancy. The V1Hf single vacancy and V1Hf+1S divacancy induce magnetic moments of 3.265 and 2.000 μB, respectively, whereas the V1S single vacancy and V1Hf+2S trivacancy do not induce any magnetic moments. One of the group‐VIB and VIIB transition metal atoms substituting for one Hf atom in the monolayer HfS2 induces magnetic moments of about 2.000 and 3.000 μB, respectively. Furthermore, the spin‐polarized band structures show that the Cr‐doped monolayer HfS2 is a magnetic metal, whereas the Mn‐, Tc‐, and Re‐doped monolayer HfS2 are magnetic semiconductor. The Mo‐ and W‐doped monolayer HfS2 are magnetic half metal with wide spin‐down bandgaps of 0.975 and 1.074 eV, respectively, and thus can be used in nanoelectronics and spintronics devices. [ABSTRACT FROM AUTHOR]

A reconfigurable magnetorquer coil has been designed and implemented for the CubeSat power management, attitude determination, and control tile (CubePMT) module of CubeSat-standard nanosatellites. Magnetorquer coil is a good choice for attitude control and stabilization of nanosatellites. The goal of this work is to provide CubeSat with a magnetorquer coil, which has small dimensions, low weight, and low heat dissipation. The designed magnetorquer coil is reconfigurable and integrated within the printed circuit board internal layers, occupying no extra space on CubeSat. Coils in each layer are treated separately and can be attached and detached through straps. Changing the arrangement of these straps, one can use 1, 2, 3, or 4 coils in series, parallel, or any hybrid combination. This reconfigurable design provides an option for generating different amounts of magnetic moment and resultant torque to stabilize and rotate the satellite. Emissivity of the CubePMT module was found through lab experiments. Power dissipation and the corresponding temperature increase of the CubePMT module are evaluated by thermal modeling. [ABSTRACT FROM PUBLISHER]

We investigate the effect of vacancies and doping on the electronic, magnetic and optical properties of 1T-SnSe 2 monolayer by using density functional theory calculations. The results reveal that the semiconducting 1T-SnSe 2 monolayer becomes a half-metal on creating one tin vacancy (V 1Sn), while it is still a semiconducting on creating one selenium vacancy (V 1Se), two selenium vacancy (V 2Se), as well as one tin and one selenium vacancy (V 1Sn+1Se). The V 1Sn and V 1Sn+1Se vacancies induce magnetic ground states with net magnetic moments of 4 and 2 μ B respectively, while the V 1Se and V 2Se vacancies induce nonmagnetic ground states. In Mo-doped 1T-SnSe 2 monolayer, crystal-field splitting of Mo-4d orbital in the octahedral environment induces net magnetic moment of 2 μ B. The band structure and density of states also show that the Mo-doped system is a magnetic semiconductor. In addition, the defective 1T-SnSe 2 mononlayer can also enhanced the absorption efficiency of the solar energy, particularly in the infrared region. An interesting red-shift phenomenon has been observed in the curves of imaginary part of the dielectric function and absorption spectra for the defect systems, suggesting their quite promising applications in optoelectronic devices. The top view atomic models of 1T-SnSe 2 monolayer with (a) V 1Sn vacancy, (b) V 1Se vacancy, (c) V 1Sn+1Se vacancy, (d) V 2Se vacancy and (e) Mo-doped. Image 1 • 1T-SnSe 2 monolayer with a V 1Sn vacancy change to a half-metal. • V 1Sn vacancy and V 1Sn+1Se vacancy induce moments 4 and 2 μ B , respectively. • Mo-doped 1T-SnSe 2 monolayer is a magnetic semiconductor with 2μ B moment. • Defect systems enhance the absorption efficiency of the solar energy. • Defects study provides a promising platform for optoelectronic device applications. [ABSTRACT FROM AUTHOR]

• It is easily to dope 5d TM atoms into monolayer SnS 2 under S-rich condition. • W, Re, Os, Ir, Pt, Au, Hg-doped monolayer SnS 2 have moments 2, 3, 2, 1, 0, 1, 2µ B. • W, Re, Hg-doped monolayer SnS 2 systems are magnetic semiconductors. • Os, Ir, Au-doped monolayer SnS 2 are magnetic half-metallic useable in spintronics. We explore the structural, electronic and magnetic properties of the monolayer SnS 2 systems doped with 5d transition metals (TM) atoms X (X = W, Re, Os, Ir, Pt, Au or Hg) using first-principles approach. The formation energies show that these materials can be easily fabricated under the S-rich experimental condition. The spin-polarized phases are more favorable than non spin-polarized phases. The pristine monolayer SnS 2 is a nonmagnetic semiconductor with an indirect band gap of 1.579 eV, the 5d TM atoms X (X = W, Re, Os, Ir, Pt, Au or Hg) doped monolayer SnS 2 systems have the total magnetic moments of 2, 3, 2, 1, 0, 1, 2 µ B , respectively, because the octahedral coordinated six S ligands bring in a larger crystal field splitting than exchange splitting onto the 5d TM atoms X. Furthermore, the spin-polarized band structures show that the W, Re or Hg-doped monolayer SnS 2 systems are magnetic semiconductors, but the Os, Ir or Au-doped monolayer SnS 2 systems are magnetic half-metallic with the wider band gaps of 1.509, 1.632 or 1.383 eV respectively in one of the two spin channels, and thus are useable in spintronic fields. [ABSTRACT FROM AUTHOR]

An attitude control system (ACS) is one of the critical subsystems of any spacecraft and typically is in charge of de-tumbling, controlling, and orienting the satellite after initial deployment and during the satellite operations. The magnetorquer is a core magnetic attitude control actuator and, therefore, a good choice for nanosatellite attitude stabilization. There are various methods to achieve control torque using the magnetorquer. An innovative design of a printed magnetorquer has been proposed for the nanosatellites, which is modular, scalable, cost effective, less prone to failure, with reduce harness and power consumption since the traces are printed either on the top layer or inner layers of the printed circuit board. The analysis in terms of generated torque with a range of input applied voltages, trace widths, outer and inner-most trace lengths is presented to achieve the optimized design. The optimum operating voltage is selected to generate the desired torque while optimizing the torque to the power ratio. The results of the analysis in terms of the selection of optimized parameters, including torque to power ratio, generated magnetic dipole moment, and power consumption, have been validated practically on a CubeSat panel. The printed magnetorquer configuration is modular which is useful to achieve mission level stabilization requirements. For spin-stabilized satellites, the rotation time analysis has been performed using the printed magnetorquer. [ABSTRACT FROM AUTHOR]

We use the first-principle methods to systematically study the structural, electronic, magnetic and optical characteristics of the perfect and Co-X (X = B, C, N, O or F) codoped single-layer WS 2. The results show that firstly, all Co-X (X = B, C, N, O or F) codoped single-layer WS 2 are easier to form in S-rich environment than in W-rich environment. Second, although the perfect single-layer WS 2 is non-magnetic semiconductor (NM-SC), the Co-X (X = B, C, N or F) codoped single-layer WS 2 become to magnetic semiconductor (M − SC) with magnetic moments 2, 3, 2 or 2 μ B , while the Co–O codoped single-layer WS 2 transforms to magnetic half metal (M-HM) with magnetic moment 1 μ B. Thirdly, comparing with the perfect single-layer WS 2 , the Co-X (X = B, C, N, O or F) codoped single-layer WS 2 show not only the red-shifted absorption edges but also enhanced absorption rate in infrared and visible light region, implying the Co-X (X = B, C, N, O or F) codoped single-layer WS 2 have great application prospects in infrared and visible light detection. (a) Top and (b) left-side views of Co-X (X = B, C, N, O or F) codoped single-layer WS 2 with a 4 × 4 × 1 supercell. The gray, yellow, blue and red balls denote W, S, Co and X atoms, respectively. For clarity, the left-side view (b) is plotted after the left W–S zigzag chain is removed. [Display omitted] [ABSTRACT FROM AUTHOR]

• V 1Zr (V 1Zr+1Se) defected ZrSe 2 monolayer is magnetic metal with moment 1.756 (1.295) µ B. • V 1Se (V 1Zr+2Se) defected ZrSe 2 monolayer is nonmagnetic metal (semiconductor). • Cr- (Mo-) doped ZrSe 2 monolayer is magnetic metal with moment 2.482 (2.130) µ B. • Mn- (Tc-, Re-) doped ZrSe 2 monolayer is magnetic semiconductor with moment 3.000 (2.999, 2.999) µ B. • W-doped ZrSe 2 monolayer is magnetic half-metal with moment 2.000 µ B and useable in spintronics. Based on the first-principles under the framework of density functional theory, we report the studies of vacancy defects and substitution doping on the electronic and magnetic characteristics of ZrSe 2 monolayer (ZrSe 2 -ML). The results reveal that the non-magnetic semiconductor (SC) material ZrSe 2 has magnetic metal behavior by producing one Zr vacancy (V 1Zr) as well as one Zr and one Se di-vacancy (V 1Zr+1Se), the net moments are 1.756 and 1.295 μ B , and both originate from the Se atoms around the vacancies. The one Se vacancy (V 1Se) system exhibits the metal behavior, while the one Zr and two Se tri-vacancy (V 1Zr+2Se) system still maintains the characteristics of a non-magnetic SC. In addition, a transition metal (TM) atom X is used to replace one Zr atom in the non-magnetic SC material ZrSe 2 , which can also induce magnetism or has metallic behavior. The Cr-, Mn-, Mo-, Tc-, W- and Re-doped systems exhibit the magnetic behavior with moments are 2.482, 3.000, 2.130, 2.999, 2.000, 2.999 μ B , respectively. The moments are proportional to the number of unpaired electrons remaining on the d orbitals of TM atoms. These systems have metallic characteristic of Cr- and Mo-doped. The Mn-, Tc- and Re-doped systems still maintain SC characteristic. In particular, the W-doped ZrSe 2 -ML is half-metal. The calculated values show that under the condition of Se-rich, it is energetically favorable and relatively easy to dope TM atom into ZrSe 2 -ML. [ABSTRACT FROM AUTHOR]

• The Mn-O codoping under the Se-rich condition is the most stable. • The codoped systems are all magnetic with total magnetic moments of 1.00 µB. • The Mn-Se and Mn-Te codoped monolayer WSe 2 change to magnetic half-metal. • A significant optical anisotropy appears in the monolayer WSe 2 systems. • A red-shift phenomenon has been observed in ε 2 (ω) and α(ω) for the Mn-X codoping. The structural, magnetic, electronic and optical properties of the pure and Mn-X (X = O , S, Se or Te) codoped monolayer WSe 2 systems are quantitatively examined through first-principles calculations. The lower formation energy under Se-rich condition shows that the codoped systems under Se-rich condition is more stable than W-rich condition, especially the Mn-O codoping is the most stable with the minimum formation energy -2.08 eV. Although the pure monolayer WSe 2 is a nonmagnetic semiconductor, the codoped systems are all magnetic with total magnetic moments of 1.00 µ B due to the introduced one unpaired electron. It is worth mentioning that the Mn-Se and Mn-Te codoping make the monolayer WSe 2 display magnetic half-metallic properties. Finally, the optical properties of the pure and codoped monolayer WSe 2 are studied in x (parallel to the WSe 2 plane) and z (perpendicular to the WSe 2 plane) directions. An interesting red-shift phenomenon has been observed in the curves of imaginary part of the dielectric function and absorption spectra for the Mn-X codoping, suggesting their quite promising applications in optoelectronic devices. [ABSTRACT FROM AUTHOR]

Exploring highly spin-polarized materials is crucial for the development of spin-based devices. In this paper, we investigate the atomic structure, electronic, half-metallic and magnetic properties of the CsCrZ 2 (Z = O, S, Se or Te) Heusler alloys, by performing first-principles calculations based on density functional theory (DFT). The geometry optimization process shows that the alloys are more stable in Cu 2 MnAl type structure than in Hg 2 CuTi one. To find a magnetic ground state, the total energy of the alloys is calculated in the non-magnetic (NM), ferromagnetic (FM) and anti-ferromagnetic (AFM) ordering. We find that, the FM ordering yields the lowest energy, thereby confirming that the alloys are FM in the ground state. On computing the cohesive and formation energy in the ground state, it is found that alloys are chemically and thermodynamically stable, respectively. Spin polarized band structures and density of states (DOS) demonstrate that the CsCrO 2 , CsCrS 2 and CsCrSe 2 alloys are true half-metals with 100% spin-polarization at the Fermi level, while the CsCrTe 2 alloy is predicted as highly spin polarized material. Furthermore, the CsCrO 2 , CsCrS 2 and CsCrSe 2 alloys possess 2.529, 2.250 and 2.050 eV gaps in the spin down band structure, respectively. The calculated total magnetic moments reveal that half-metallic alloys have an integral total magnetic moment of 3.000 μ B , which satisfies the Slater-Pauling rule M t = Z t -16. The main contribution to the total magnetic moment comes from the Cr atoms (about 3.9 μ B). Furthermore, the Curie temperature T C calculated within classical Heisenberg model is estimated to be about 822 K (CsCrO 2), 685 K (CsCrS 2), 753 K (CsCrSe 2) and 636 K (CsCrTe 2). The obtained high spin polarization and above room temperature FM ordering make the materials as promising materials to be used in spintronic technology. Electron localized function (ELF) maps for (a) (0 0 1) plane, (b) (1 0 1) plane in CsCrO 2 Heusler alloy. Image 1 • The CsCrZ 2 (Z = O, S, Se and Te) Heusler alloys are all stable in FM ground state. • The CsCrZ 2 Heusler alloys satisfies the Slater-Pauling rule M t = Z t -16. • The CsCrO 2 , CsCrS 2 and CsCrSe 2 alloys are true half-metals with 100% spin-polarization. • The CsCrTe 2 alloy is a nearly half-metal and predicted as highly spin polarized material. [ABSTRACT FROM AUTHOR]