Transition metal ions magnetic properties

In an ionic compound, the partial covalence of a bond formed between a transition metal ion and its ligand modifies the magnetic properties of the cation. It can be seen, for example, that if electrons were... 

Oxides play many roles in modem electronic technology from insulators which can be used as capacitors, such as the perovskite BaTiOs, to the superconductors, of which the prototype was also a perovskite, Lao.sSro CutT A, where the value of x is a function of the temperature cycle and oxygen pressure which were used in the preparation of the material. Clearly the chemical difference between these two materials is that the capacitor production does not require oxygen partial pressure control as is the case in the superconductor. Intermediate between these extremes of electrical conduction are many semiconducting materials which are used as magnetic ferrites or fuel cell electrodes. The electrical properties of the semiconductors depend on the presence of transition metal ions which can be in two valence states, and the conduction mechanism involves the transfer of electrons or positive holes from one ion to another of the same species. The production problem associated with this behaviour arises from the fact that the relative concentration of each valence state depends on both the temperature and the oxygen partial pressure of the atmosphere. 

The lanthanides have electrons in partly filled 4/orbitals. Many lanthanides show colors due to electron transitions involving the 4/orbitals. However, there is a considerable difference between the lanthanides and the 3d transition-metal ions. The 4/ electrons in the lanthanides are well shielded beneath an outer electron configuration, (5.v2 5p6 6s2) and are little influenced by the crystal surroundings. Hence the important optical and magnetic properties attributed to the 4/ electrons on any particular lanthanide ion are rather unvarying and do not depend significantly upon the host structure. Moreover, the energy levels are sharper than those of transition-metal ions and the spectra resemble those of free ions. 

In the initial state, all transition-metal ions are in the low-spin state, giving an effectively nonmagnetic solid. Irradiation transfers an electron from Fe to Co and promotes electron excitation to create all high-spin ions with a considerable magnetic moment (Fig. 9.29b). The magnetic defects in this case are the triple group of metal ion-cyanide-metal ion. As in all materials for device use, variation in dopant concentrations can be used to tune the desirable properties of the solid. 

Carbonate has proved to be a versatile ligand. Its coordination mode expands from 1 to 6, the last one is visualized when each atom binds two metal ions simultaneously. In recent years, significant progress has been made in the synthesis, structure, and magnetic properties of polynuclear carbonato complexes of transition metal ions. Such studies have also been extended to lanthanides and actinides. The speciation studies of these metal ions in aquatic environments in the presence of carbonate have resulted in significant... 

Magnetic properties of some transition-metal ions... 

Considerable interest centres on the Mantle constituting, as it does, more than half of the Earth by volume and by weight. Attention has been focussed on several problems, including the chemical composition, mineralogy, phase transitions and element partitioning in the Mantle, and the geophysical properties of seismicity, heat transfer by radiation, electrical conductivity and magnetism in the Earth. Many of these properties of the Earth s interior are influenced by the electronic structures of transition metal ions in Mantle minerals at elevated temperatures and pressures. Such effects are amenable to interpretation by crystal field theory based on optical spectral data for minerals measured at elevated temperatures and pressures. 

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