ISSN:
1434-6036
Source:
Springer Online Journal Archives 1860-2000
Topics:
Physics
Notes:
Abstract There is increasing interest in the charge transport properties of crystals which contain identical magnetic nuclei, but with ions of different valence states. A particularly interesting example is a Eu2+ – Eu3+ pair, for both ions are insensitive to crystal fields, so there is no electrostatic hindrance to electron transfer. The problem of setting up a suitable description of such a pair, particularly when separated by an intervening non-magnetic ion, such as S2-, presents a number of difficulties. The paper discusses these, for a Eu2+ – S2- – Eu3+ “molecule”, in which the europium nuclei are regarded as fixed, but the sulphur ion can move. It is shown that if the S2- is regarded as fixed the transfer mechanism will be a second order process, probably involving transfer of a sulphur electron on to a Eu3+. However when the sulphur is not fixed new first order processes are introduced, and the previous second order processes are modified. There is then the possibility that, for the low-lying states, the transfer can be quenched, in which case the S2- ion will appear to be attached to a specific europium ion, which will be Eu3+. It is suggested that the theory may be relevant to certain metal-insulator transitions in which changes occur from relatively free electron transfer to ordered arrangements of identical ions, for it includes the possibility of detailed descriptions of the orbital and spin states of the magnetic ions.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01313907
