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|Title:||Resistance noise in giant magnetoresistive materials|
|Author(s):||Hardner, Heidi Theresa|
|Doctoral Committee Chair(s):||Klein, Miles V.|
|Department / Program:||Physics|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Subject(s):||Physics, Condensed Matter|
|Abstract:||We have studied resistance noise in a variety of systems exhibiting giant magnetoresistance (GMR) including coupled and uncoupled multilayers, spin-valves and granular systems. Large equilibrium 1/f noise in the resistance of these materials is associated with the GMR effect. One consequence was that we were able to use the out-of-phase response of the resistance to a magnetic field in an antiferromagnetically coupled GMR multilayer to make the first quantitative prediction of the 1/f noise in a resistor using the fluctuation-dissipation relation.
Interest in GMR materials has been fueled by their tremendous potential for applications involving sensing magnetic fields. The large noise we have observed could potentially thwart very sensitive devices and we have developed a figure of merit with which to compare the sensitivity of various materials in situations where 1/f noise is the relevant background. Using this scheme we have compared various GMR materials to each other and to existing permalloy devices.
In addition, we have used a non-equilibrium noise measurement to probe the domain sizes and structure of various GMR materials. We have observed an interesting field-history dependence in the domain structure in multilayered materials and have demonstrated that the magnetic domains in these materials can be quite large and possibly limited by patterning.
Finally, recent measurements on a system exhibiting colossal magnetoresistance (CMR) are presented. Large non-Gaussianity which we have observed in the resistance noise has the potential to discriminate among various theoretical descriptions of the conduction in this system.
|Rights Information:||Copyright 1996 Hardner, Heidi Theresa|
|Date Available in IDEALS:||2011-05-07|
|Identifier in Online Catalog:||AAI9702531|