Alternate Author Name(s)

Ronald Gary Pirich

Document Type

Dissertation

Date of Award

1976

Keywords

Valence (Theoretical chemistry), Magnesium alloys, Magnetic susceptibility

Degree Name

Doctor of Philosophy (PhD)

Department

Physics

First Advisor

Charles R. Burr

Second Advisor

Clifford E. Myers

Third Advisor

Robert L. Pompi

Abstract

An experimental investigation has been performed on a series of MgEu alloys, ranging in concentration from 46 ppm to 33.84 a/o Eu, in order to study the possibility of a valence transition occurring in this system. Part of the experimental study was performed in collaboration with Dr. Gopal Shenoy of Argonne National Laboratory.

In view of the importance of crystallographic and metallurgical structures in valence transitions, the study not only encompassed the magnetic and electronic characterization of this system but also the elastic, crystallographic, thermal, transport, metallurgical and phase properties as well.

This experimental study revealed three significant features of the MgEu system:

  1. The onset of some sort of magnetic ordering at low temperatures, among whose consequences is the appearance of a new intermetallic structure which may be metastable.
  2. A pure configuration crossover of certain Eu ions due to cold-work has been observed for the first time. This valence transition appears to be of the inhomogeneous, mixed Valence type.
  3. The apparent enhancement of the Eu(2+) moment has been observed for the first time. The degree of enhancement seems to be dependent on the structure of the intermetallic compounds found in the MgEu system and appears to scale linearly with Eu concentration.

This paper presents the methods of sample preparation and analysis used in this investigation as well as a formal discussion of results and proposed models to explain the observed phenomena.

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