Magnetism in Au-Supported Planar Silicene

The adsorption and substitution of transition metal atoms (Fe and Co) on Au-supported planar silicene have been studied by means of first-principles density functional theory calculations. The structural, energetic and magnetic properties have been analyzed. Both dopants favor the same atomic configurations with rather strong binding energies and noticeable charge transfer. The adsorption of Fe and Co atoms do not alter the magnetic properties of Au-supported planar silicene, unless a full layer of adsorbate is completed. In the case of substituted system only Fe is able to produce magnetic ground state. The Fe-doped Au-supported planar silicene is a ferromagnetic structure with local antiferromagnetic ordering. The present study is the very first and promising attempt towards ferromagnetic epitaxial planar silicene and points to the importance of the substrate in structural and magnetic properties of silicene.

Identification of Material Properties and Optimal Design of Magnetically Shielded Rooms

In this paper, we propose an optimal design procedure for magnetically shielded rooms. Focusing on multi-layer ferromagnetic structures, where inner layers operate at very low magnetic field, we propose an identification method of the magnetic material characteristic in the Rayleigh region. A numerical model to simulate the shielding efficiency of a multi-layer ferromagnetic structure is presented and experimentally tested on different geometries and layer configurations. The fixed point iterative method is adopted to handle the nonlinearity of the magnetic material. In conclusion, the optimization of the design parameters of a MSR is discussed, using the Vector Immune System algorithm to minimize the magnetic field inside the room and the cost of the structure. The results highlight that a linear magnetic characteristic for the material is sufficient to identify the suitable geometry of the shield, but the nonlinear model in the Rayleigh region is of fundamental importance to determine a realistic shielding factor.

Field-Induced Transitions in Highly Frustrated SrHo2O4

SrHo 2O 4 is a geometrically frustrated magnet in which the magnetic Ho 3 + ions are connected through a network of zigzag chains and coupled by several competing interactions. The Ho 3 + ions show a pronounced Ising anisotropy at low temperatures, and the spins on the two crystallographically inequivalent magnetic sites point along orthogonal crystallographic axes. Using single-crystal neutron diffraction, we report on the development of complex and highly anisotropic short- and long-range magnetic order in SrHo 2O 4 induced by an applied magnetic field. For H ‖ c , the diffuse scattering around the k = 0 positions is suppressed and above 0.5 T the spin structure for one of the Ho sites is long-range and ferromagnetic. For H ‖ b , planes of diffuse scattering at Q = ( h k ± l 2 ) are split by the field, and an up–up–down magnetic order associated with a 1/3-magnetisation plateau develops at 0.8 T. Further increasing the field above 1.2 T allows the second Ho site to also order in a long-range ferromagnetic structure.