A kind of tunable magnetic fluid grating is developed in this letter. The operating principle of the tunable magnetic fluid grating is analyzed theoretically. When the absorption coefficient modulation of the grating is not too large, the energy of the zeroth-order diffracted light can be transferred to that of the higher-order completely and vice versa. Experiments are done to investigate the tunable diffraction properties of the magnetic fluid grating, and the transfer of the energy of the zeroth-order diffracted light to that of the higher-order is apparent.
Under proper growth conditions, ordered and uniform Mn nanodots were fabricated on the Si(111)-7×7 surface without the presence of a wetting layer. Furthermore, the Mn nanodots deposited onto the elevated substrates were observed to occupy preferentially on the faulted half unit cells (FHUCs) of the Si(111)-7×7 surface. This phenomenon implies that the Mn dots adsorbed on the FHUCs is more stable than those adsorbed on the unfaulted half unit cells (UFHUCs). Within the framework of quasiequilibrium thermodynamics, the energy difference between adsorption on the UFHUCs and the FHUCs was estimated to be 0.05±0.01 eV. The intrinsic attractive potential wells on the FHUCs effectively trap the outdiffusion of Mn atoms, and consequently result in a preferential arrangement of islands with well-defined sizes.Artificially controllable fabrication of nanostructures on supporting substrates with atomic precision has long been a subject of fundamental and applied science research [1][2][3][4][5].Recently, ordered and identical Indium, Gallium, Aluminum and Cobalt nanoclusters have been fabricated by using silicon surfaces as templates [6][7][8][9]. Although the uniform magnetic clusters can be grown on insulating substrates [10,11], up to date, highly ordered and uniform ferro-, ferri, and antiferromagnetic nanodots on the supporting Si (111) substrates have not yet been achieved. In this work, the Si(111)-7×7 reconstructed surface was employed as a template to grow monodispersed Mn nanodots. The reasons for choosing Mn deposition on the Si(111)-7×7 are followings: (1)Mn is a unique element in the 3d transition metal series and small Mn clusters are expected to possess anomalous magnetic properties [12]; (2)The uniform nanodots grown on semiconducting substrates without a wetting layer are often desirable for electronic and magnetic device applications. It was found that three dimensional (3D) Mn islands were immediately formed on the Si(111) surface without the presence of a wetting layer(the Volmer-Weber (VW) growth mode)[13]. Furthermore, the periodic pattern of the reconstructed Si(111)-7×7 lattice has the potential to confine the Mn clusters growth and results in a uniform and ordered array of clusters. (3)Comparing with other magnetic metals, such as Fe [14], and Co [9] on Si (111), Manganese silicates are not easy to form at room temperature, even at elevated temperatures. Therefore, it provides a unique opportunity for investigating the low dimensional magnetism of metallic nanodots. By delicate control of the
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