Showing papers by "Myriam P. Sarachik published in 1988"
TL;DR: In this article, the authors have made static susceptibility measurements at temperatures between 1.25 and 300 K on samples of phosphorus-doped silicon with dopant concentrations in the range 0.2 and 1.3, where n is the critical concentration for the metal-insulator transition.
Abstract: We have made static susceptibility measurements at temperatures between 1.25 and 300 K on samples of phosphorus-doped silicon with dopant concentrations in the range 0.2/${n}_{c}$1.3, where ${n}_{c}$ is the critical concentration for the metal-insulator transition. In this paper we discuss our results for the diamagnetism associated with the donor electrons. We find that the donor susceptibility above 60 K is diamagnetic and varies linearly with concentration. We associate the susceptibility observed at these temperatures with a diamagnetic term, ${\ensuremath{\chi}}_{D}$(T,n), which is of the Landau-Peierls-Pauli type, but which is linear in n. Using static susceptibility data at higher concentrations obtained by other investigators, we show that the linear behavior of ${\ensuremath{\chi}}_{D}$ persists up to \ensuremath{\sim}3${n}_{c}$, i.e., within the entire impurity-``band'' region, beyond which it reverts to the ${n}^{1/3}$ behavior expected for a standard band. We find that published ESR susceptibility data for similar concentrations exhibit the same concentration dependence as ${\ensuremath{\chi}}_{D}$. Use of the ESR data has enabled us to separate out the orbital and spin contributions to the susceptibility. The average diamagnetic susceptibility per donor is found to agree with calculated values of the Larmor diamagnetism of localized electrons, and is independent of concentration over a range spanning the transition from insulating to metallic behavior; so far as the average orbital contribution of the donor electrons in the impurity ``band'' is concerned, it makes little difference whether the electrons are in localized or extended states. In addition to their possible implications for the nature of the impurity ``band,'' these results are important in that they provide a baseline against which donor susceptibility can be measured in order to determine a contribution at low temperatures which may be attributed to the presence of local moments across the metal-insulator transition.
23 citations
TL;DR: The smooth continuation of the same behavior onto the metallic side of the transition suggests that local moments exist in metallic Si:P, which may imply that the exchange interaction between the magnetic moments does not undergo any abrupt or major change in character as the transition is crossed.
Abstract: For donor concentrations on both sides of the metal-insulator transition, the paramagnetic component of the susceptibility of Si:P at low temperature is described by a power law approx.T/sup -//sup ..cap alpha../, modified by a term which represents thermal activation to higher-energy states which are magnetically inert. For insulating samples, the power law is associated with the random Heisenberg antiferromagnet. The smooth continuation of the same behavior onto the metallic side of the transition suggests that local moments exist in metallic Si:P. We further suggest that this may imply that the exchange interaction between the magnetic moments does not undergo any abrupt or major change in character as the transition is crossed, in spite of the appearance of delocalized electrons.
17 citations
TL;DR: The resistivity and the Hall coefficient of indium-doped cadmium selenide with carrier concentrations spanning the insulator-to-metal transition have been measured and it is demonstrated that use of the Hall mobility deduced from these data and careful analysis and application of recent theory yield an estimate of the degree of compensation.
Abstract: The resistivity and the Hall coefficient of indium-doped cadmium selenide with carrier concentrations spanning the insulator-to-metal transition have been measured as a function of temperature. We demonstrate that use of the Hall mobility deduced from these data and careful analysis and application of recent theory yield an estimate of the degree of compensation, K = N/sub A//N/sub D/, for metallic as well as insulating material. Combining these results with Hall coefficient measurements at room temperature, one can then estimate both the number of donors, N/sub D/, and acceptors, N/sub A/. .AE
6 citations