Polycrystalline samples of (Zn, Co) co-doped SnO 2 nanoparticles were prepared using a co-precipitation method. The influence of (Zn, Co) co-doping on electrical, dielectric, and magnetic properties was studied. All of the (Zn, Co) co-doped SnO 2 powder samples have the same tetragonal structure of SnO 2 . A decrease in the dielectric constant was observed with the increase of Co doping concentration. It was found that the dielectric constant and dielectric loss values decrease, while AC electrical conductivity increases with doping concentration and frequency. Magnetization measurements revealed that the Co doping SnO 2 samples exhibits room temperature ferromagnetism. Our results illustrate that (Zn, Co) co-doped SnO 2 nanoparticles have an excellent dielectric, magnetic properties, and high electrical conductivity than those reported previously, indicating that these (Zn, Co) co-doped SnO 2 materials can be used in the field of the ultrahigh dielectric material, high frequency device, and spintronics.
A novel variational approach is presented for the calculation of the ground-state energy of the polaron in arbitrary N dimensions in the strong-coupling limit. By using the phonon coherent state to represent the wavefunction of phonons, a self-consistent integro-differential equation for the electron wavefunction is derived. The calculated results of the ground-state energy for N = 1, 2 and 3 agree well with the best results in the literature. It is also found that, for arbitrary N, the present results are less than the Feynman path integral ones by small percentages. It is proposed that this approach should be universal for systems involving polarons in the strong-coupling regime.
The temperature dependence of the Hall coefficient RH has been measured between 50 and 250 K for the superconducting compounds with nominal compositions Bi2Ca2Sr2Cu3Oy and Bi1.6Pb0.4Ca2Sr2Cu3Oy. It is found that the Hall number, nH, is linearly T-dependent and field-independent in the normal state and decreases rapidly on doping with lead. This result is quite in agreement with the recent theoretical calculation proposed by Xing and co-workers (1988). A large anomaly in RH is observed around Tc, which is discussed in terms of the intergranular structure of this material.
The effective mass of a large polaron is calculated using the extended phonon coherent state proposed in our previous paper. In the weak-coupling limit, the mass expansion obtained can reproduce the fourth-order perturbative result. Moreover, in the intermediatecoupling range, the calculated results are in good agreement with those of other approaches.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.