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Magnetic moments in amorpous palladium-cobalt-silicon alloys

Citation

Weiner, Martin Eric (1968) Magnetic moments in amorpous palladium-cobalt-silicon alloys. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechTHESIS:07222014-134811615

Abstract

The magnetic moments of amorphous ternary alloys containing Pd, Co and Si in atomic concentrations corresponding to Pd_(80-x)Co_xSi_(20) in which x is 3, 5, 7, 9, 10 and 11, have been measured between 1.8 and 300°K and in magnetic fields up to 8.35 kOe. The alloys were obtained by rapid quenching of a liquid droplet and their structures were analyzed by X-ray diffraction. The measurements were made in a null-coil pendulum magnetometer in which the temperature could be varied continuously without immersing the sample in a cryogenic liquid. The alloys containing 9 at.% Co or less obeyed Curie's Law over certain temperature ranges, and had negligible permanent moments at room temperature. Those containing 10 and 11 at.% Co followed Curie's Law only above approximately 200°K and had significant permanent moments at room temperature. For all alloys, the moments calculated from Curie's Law were too high to be accounted for by the moments of individual Co atoms. To explain these findings, a model based on the existence of superparamagnetic clustering is proposed. The cluster sizes calculated from the model are consistent with the rapid onset of ferromagnetism in the alloys containing 10 and 11 at.% Co and with the magnetic moments in an alloy containing 7 at.% Co heat treated in such a manner as to contain a small amount of a crystalline phase. In alloys containing 7 at.% Co or less, a maximum in the magnetization vs temperature curve was observed around 10°K. This maximum was eliminated by cooling the alloy in a magnetic field, and an explanation for this observation is suggested.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Materials Science
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Materials Science
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Duwez, Pol E.
Thesis Committee:
  • Unknown, Unknown
Defense Date:15 May 1968
Record Number:CaltechTHESIS:07222014-134811615
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:07222014-134811615
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:8585
Collection:CaltechTHESIS
Deposited By: John Wade
Deposited On:22 Jul 2014 21:03
Last Modified:22 Jul 2014 21:03

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