Magnetic Behavior and Phase Transitions of Selected Pure, Dilute and Mixed Magnets

College Of William And Mary, Williamsburg VA

Investigators

Abstract

The detailed magnetic behavior, especially that associated with magnetic phase transitions, of various pure, dilute and mixed magnetic systems with short-range exchange interactions will be examined. The pure materials are interesting because: some are members of a new transition metal series certain members of which exhibit nonequilibrium behavior, one is ferromagnetic and a potential member of a rare universality class; and others show signs of very large zero-field splittings. The study of spin glass behavior in insulators is of particular importance, and several of the proposed mixed magnets could exhibit such behavior in insulators is of particular importance, and several of the proposed mixed magnets could exhibit such behavior. One of these is a potential new type of spin glass which may occur on diluting a previously studied ferromagnet of novel type. Even apart from spin glass formation, the behavior of a ferromagnet of this kind with dilution is an important problem. Two of the mixed systems are ternary in character, that is they contain more than two components. Such systems are virtually unstudied among insulating materials. The mixed magnets will contain either competing exchange interactions, competing anisotropies, different spin values, or some combination of these. Determination of magnetic phase diagrams, showing the dependence of ordering temperature on composition and regions of phase stability, is a major objective of this work. Some theoretically predicted phase diagram types are yet to be observed. Very high field magnetization data will also be obtained for several systems, both pure and mixed; this will yield new information on critical fields in the materials and on zero-field splittings. %%% The chemical compounds to be examined included novel monohydrates of simple transition metal salts that exhibit certain novel structural or magnetic features. Studies of these systems will further such materials science goals as elucidation structure-property relationships and developing materials with new properties. A major impact will be the opportunities afforded undergraduate science students to gain experience with frontier research topics in a field of high priority to industry.