Chen H.,Yancheng Teachers University |
Chen H.,Nanjing University of Aeronautics and Astronautics
Journal of Magnetism and Magnetic Materials | Year: 2012
We studied the magnetic properties of Mn/Fe codoped ZnS comparatively with and without defects using first-principle calculation. The calculated results indicate that the Mn/Fe codoped ZnS system tends to stabilize in a ferrimagnetic (FiM) configuration. To obtain a ferromagnetic (FM) configuration, we consider the doped system with defects, such as S or Zn vacancy. The calculated results indicate that the doped system with Zn vacancy favors FiM states. Although the FM states of the doped system with S vacancy are more stable than the FiM states in negative charge states, the FM states are not stable enough to exist. Finally, we replaced an S atom by a C atom in the doped system. The C atom prefers to substitute the S atom connecting Mn and Fe atoms. The formation energy of this defect is -0.40 eV, showing that Mn/Fe/C codoped ZnS can be fabricated easily by experiments. Furthermore, the FM state was lower in energy than the FiM state by 114 meV. Such a large energy difference between the FM and FiM states implies that room temperature ferromagnetism could be expected in such a system. © 2012 Elsevier B.V. All rights reserved.
Wang Z.,Yancheng Teachers University
Fuzzy Sets and Systems | Year: 2016
In this paper, we firstly discuss the deresidual operations of left (right) semi-uninorms and show which properties they satisfy. Then, we investigate the left and right semi-uninorms induced by a coimplication and give some conditions such that the operations induced by a coimplication constitute left or right semi-uninorms. Finally, we demonstrate that the meet-semilattice of all disjunctive right (left) -distributive left (right) semi-uninorms is order-reversing isomorphic to the join-semilattice of all right -distributive coimplications, which satisfy the neutrality principle. © 2015 Elsevier B.V.
Yu J.-J.,Yancheng Teachers University
International Journal of Automation and Computing | Year: 2011
This paper concerns the robust stability analysis of uncertain systems with time delays as random variables drawn from some probability distribution. The delay-distribution-dependent criteria for the exponential stability of the original system in mean square sense are achieved by Lyapunov functional method and the linear matrix inequality (LMI) technique. The proposed approach involves neither free weighting matrices nor any model transformation, and it shows that the new criteria can provide less conservative results than some existing ones. Numerical examples are given to demonstrate the effectiveness and the benefits of the proposed method. © 2011 Institute of Automation, Chinese Academy of Sciences and Springer-Verlag Berlin Heidelberg.
Chen H.,Yancheng Teachers University
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2011
We have studied the structure, electronic and magnetic properties of wurtzite (WZ) ZnS semiconductor doped with one or two C atoms using first-principles calculations. The moderate formation energy implied that C-doped ZnS could be fabricated experimentally. The total magnetic moment of the 72 atom super cell was 2.02 μB, mainly due to the 2p component of the C atom. Electronic structures showed ZnS doped with C atom was p-type half-metallic ferromagnetic (FM) semiconductor and hole mediation was responsible for the ferromagnetism. The large energy difference (154 meV) between the FM and antiferromagnetic (AFM) state implied room-temperature ferromagnetism for C-doped WZ ZnS, which has great potential in spintronic devices. © 2011 Elsevier B.V. All rights reserved.
Xie J.,Yancheng Teachers University
Journal of Magnetism and Magnetic Materials | Year: 2010
The electronic and magnetic properties of wurtzite ZnS semiconductor doped with transition metal (Cr, Mn, Fe, Co, and Ni) atoms are studied by using the first-principle's method in this paper. The ZnS bulk materials doped with Cr, Fe, and Ni are determined to be half-metallic, while those doped with Mn and Co impurities are found to be semiconducting. These doped transition metal ions have long range interactions mediated through the induced magnetic moments in anions and cations of host semiconductors. These doped ZnS-based diluted magnetic semiconductors seem to be good candidates for the future spintronic applications. © 2010 Elsevier B.V.