RESUMEN
We have investigated the electronic and finite temperature magnetic properties of germanium carbide (GeC) and ferromagnetic chromium nitride (CrN) heterobilayers by using first-principles calculations based on density functional theory with Hubbard U correction and an effective anisotropic Heisenberg spin model. The dynamical stability of different stacking formations of heterobilayers is ensured by considering the phonon spectra. All the stacking patterns show half-metallicity with an out-of-plane easy-axis ferromagnetic ground state. We find a high Curie temperature for GeC/CrN heterobilayers within the random phase approximation (RPA). In addition to the symmetric stackings, i.e., AA and AB, the electronic properties of non-symmetric stackings at three different twist angles are also analyzed. The electronic structure analysis of twisted structures demonstrates that the half-metallicity of the GeC/CrN heterobilayer is stack independent. Furthermore, we have investigated the electronic properties, magnetic anisotropy energy, Curie temperature, and spin wave spectrum in the presence of biaxial strain. It is shown that the compressive strain dramatically reduces the magnetic anisotropy energy of the GeC/CrN heterobilayer and Curie temperature, but the Curie temperature still remains well above room temperature for all strain values. The increasing values of tensile strain reduce the magnetic exchange while it increases the magnetic anisotropy energy of the heterobilayer system which enhances the Curie temperature of the structures. The monolayer CrN on the GeC with a wide band gap and commensurate lattice together with a high Tc value can be a feasible candidate for future spintronic applications.
RESUMEN
OBJECTIVE: The purpose of this study was to evaluate the effects of pre- and post-irradiation application on the shear bond strength of self-adhesive luting cements to dentin and enamel. MATERIALS AND METHODS: Thirty-two extracted human maxillary incisor teeth were used in this study. Teeth were divided into two main groups according to preparation depth (0.5 mm and 1 mm) as Group E and Group D and were divided into four subgroups according to treatment protocol (n = 12). Teeth were irradiated and preparation was done after radiation. Adhesive luting cement was placed on the irradiated enamel and dentin surface (Groups E1, D1). Preparation was done before irradiation and resin cement was placed on the irradiated enamel and dentin surface (Groups E2, D2). The resin cement was first placed on their enamel and dentin surfaces and then the specimens were irradiated (Groups E3, D3). Irradiation was done with a total dose of 60 Gy, applied in fractions over 6 weeks for each groups (2-Gy/day fractions, 5 days per week). Nonirradiated groups were determined as controls groups (Groups C1, C2). The shear bond strengths of adhesive luting cement were examined. RESULTS: According to the two-way ANOVA results, depth of preparation and treatment protocol and their interactions were significant on shear bond strength of resin cement (P Conclusions: This study detected significant differences between the irradiated and nonirradiated groups, probably due to the changes in the crystalline structure of dental hard tissues.