Using the nonequilibrium Green's function method and nonequilibrium molecular dynamics simulations, we discuss the possibility of using silicene nanoribbons (SiNRs) as high performance thermoelectric materials. It is found that SiNRs are structurally stable if the edge atoms are passivated by hydrogen, and those with armchair edges usually exhibit much better thermoelectric performance than their zigzag counterparts. The room temperature ZT value of armchair SiNRs shows a width-dependent oscillating decay, while it decreases slowly with increasing ribbon width for the zigzag SiNRs. In addition, there is a strong temperature dependence of the thermoelectric performance of these SiNRs. Our theoretical calculations indicate that by optimizing the doping level and applied temperature, the ZT value of SiNRs could be enhanced to as high as 4.9 which suggests their very appealing thermoelectric applications.

Unrestricted Hartree-Fock calculations on La 1Ϫx Ca x MnO 3 (xϭ0.5 and xϭ0.67) in the full magnetic unit cell show that the magnetic ground states of these compounds consist of ''ferromagnetic molecules'' or polarons ordered in herring-bone patterns. Each polaron consists of either two or three Mn ions separated by O Ϫ ions with a magnetic moment opposite to those of the Mn ions. Ferromagnetic coupling within the polarons is strong, while coupling between them is relatively weak. Magnetic moments on the Mn ions range between 3.8 b and 3.9 B in the xϭ0.5 compound and moments on the O Ϫ ions are Ϫ0.7 B . Each polaron has a net magnetic moment of 7.0 B , in a good agreement with recently reported magnetization measurements from electron microscopy. The polaronic nature of the electronic structure reported here is obviously related to the Zener polaron model recently proposed for Pr 0.60 Ca 0.40 MnO 3 on the basis of neutron-scattering data.

Well-dispersed uniform cobalt ferrite nanoparticles were synthesized by thermal decomposition of a metal-organic salt in organic solvent with a high boiling point. Some of the nanoparticles were diluted in a SiO2 matrix and then the undiluted and diluted samples were characterized and their magnetic behavior explored. The undiluted and diluted samples exhibited maximum coercivity Hc of 23,817 and 15,056 Oe at 10 K, respectively, which are the highest values reported to date, and the corresponding ratios of remanence (Mr) to saturation (Ms) magnetization (Mr/Ms) were as high as 0.85 and 0.76, respectively. Interestingly, the magnetic properties of the samples changed at 200 K, which was observed in magnetic hysteresis M(H) loops and zero-field cooling curves as well as the temperature dependence of Hc, Mr/Ms, anisotropy, dipolar field, and the magnetic grain size. Below 200 K, both samples have large effective anisotropy, which arises from the surface spins, resulting in large Hc and Mr/Ms. Above 200 K, the effective anisotropy decreases because there is no contribution from surface spins, while the dipolar interaction increases, resulting in small Hc and Mr/Ms. Our results indicate that strong anisotropy and weak dipolar interaction tend to increase Hc and Mr/Ms, and also clarify that the jumps around H = 0 in M(H) loops can be attributed to the reorientation of surface spins. This work exposes the underlying mechanism in nanoscale magnetic systems, which should lead to improved magnetic performance.

In this paper, a highly deuterated potassium dihydrogen phosphate (DKDP) crystal with sizes up to 318 mm × 312 mm × 265 mm was grown by the rapid-growth method. The synthesis tank device was specially designed to synthesize a higher deuterium concentration and high-purity DKDP solution. The deuterium content of the as-grown crystal, which was 97.9%, was determined by two methods, including infrared (IR) spectroscopy and thermo-gravimetric analysis (TGA) measurements. The performances of the 97.9% DKDP crystal, including transmission, absorption coefficient, and laserinduced damage threshold (LIDT) were measured. The results indicate that, in the near-infrared band, the transmission of the 97.9% DKDP crystal is higher than that of KDP and 70% DKDP crystals, and the absorption coefficient is lower. The LIDT of the crystal reached 23.2 J · cm −2 (R-on-1, 1064 nm, 3 ns), which meets the engineering requirements for use in optical applications.