Theoretical studies of the EPR parameters for Ni2+ and Co+ in MgO

Abstract

The electron paramagnetic resonance (EPR) parameters (g factors and the hyperfine structure constants) for Ni 2+ and Co + in MgO are theoretically studied from the perturbation formulas of these parameters for a 3d 8 ion in octahedral crystal-fields. In the computations, the ligand orbital and spin-orbit coupling contributions are taken into account using the cluster approach. The calculated EPR parameters are in good agreement with the experimental data. The larger g factor and the smaller magnitude of the hyperfine structure constant for Ni 2+ as compared with those for Co + can be attributed to the higher spin-orbit coupling coefficient and the lower dipolar hyperfine structure parameter of the former, respectively.

Effect of Basic Promoters on Porous Supported Alumina Catalysts for Acetins Production

“…At the magnetic field, the strong resonance located in the 2400-5000 G range is attributable to the paramagnetic Ni 2+ species from the small NiO particles [48,49]. The g value close to 2.2 is assigned to either small ferromagnetic Ni clusters or the substitutional cubic Ni 2+ ions in oxides matrix [48,49]. These Ni 2+ species in such a low NiO amount on the surface could be strongly interacting with the alumina, as further demonstrated by the XPS results.…”

“…On the contrary, the EPR spectra of the supported solids depict asymmetric resonance signals in two distinct regions (Figure 7a). At the magnetic field, the strong resonance located in the 2400-5000 G range is attributable to the paramagnetic Ni 2+ species from the small NiO particles [48,49]. The g value close to 2.2 is assigned to either small ferromagnetic Ni clusters or the substitutional cubic Ni 2+ ions in oxides matrix [48,49].…”

Challenges for exploiting nanomagnet properties on surfaces

“…Additionally, thin (less than 100 nm) layers of Au or other metals are also transparent to microwaves. All these materials can contain impurities that can give signals detectable by EPR and that can be stronger than the signal from the molecular qubits deposited on the surface 54 , 55 The pulsed experiments to detect T 1 and T 2 should be possible providing that the dipolar interactions in the monolayer are less relevant than in the bulk solid. Magnetic dilution in the monolayer to avoid dipolar interactions that may cause decoherence is possible if a suitable diamagnetic analogue exists, but of course this adds extra complications to the system since the number of spins on the surface might then be too low for detection.…”