Skip to content Skip to navigation
University of Warwick
  • Study
  • |
  • Research
  • |
  • Business
  • |
  • Alumni
  • |
  • News
  • |
  • About

University of Warwick
Publications service & WRAP

Highlight your research

  • WRAP
    • Home
    • Search WRAP
    • Browse by Warwick Author
    • Browse WRAP by Year
    • Browse WRAP by Subject
    • Browse WRAP by Department
    • Browse WRAP by Funder
    • Browse Theses by Department
  • Publications Service
    • Home
    • Search Publications Service
    • Browse by Warwick Author
    • Browse Publications service by Year
    • Browse Publications service by Subject
    • Browse Publications service by Department
    • Browse Publications service by Funder
  • Help & Advice
University of Warwick

The Library

  • Login
  • Admin

Magnetic properties of Gd-Y and Gd-Sc alloys

Tools
- Tools
+ Tools

Melville, Richard John (1989) Magnetic properties of Gd-Y and Gd-Sc alloys. PhD thesis, University of Warwick.

[img]
Preview
PDF
WRAP_Theses_Melville_1989.pdf - Submitted Version - Requires a PDF viewer.

Download (5Mb) | Preview
Official URL: http://webcat.warwick.ac.uk/record=b3169870~S15

Request Changes to record.

Abstract

The magnetic structures and behaviour of Gd-Y and Gd-Sc random alloys have been investigated by single crystal neutron diffraction, ultrasonic measurements of the crystal elastic constants and resistivity measurements. The composition of the alloys studied was chosen in order to observe the competition between the ferromagnetism favoured by Gd-rich alloys and helimagnetism favoured by dilution with Y or Sc.

Neutron diffraction studies of Gd₆₀Y₄₀ and Gd₆₆Y₃₄ have been concerned principally with the helimagnetic/ferromagnetic transition. Of particular interest has been the behaviour of the modulation wavevector when the ferromagnetic phase is approached as the temperature is lowered. A novel approach to peak-fitting of the diffraction profiles for Gd₆₆Y₃₄ has enabled helical inter-layer turn angles of less than 1° to be measured, and no evidence has been observed for any discontinuity of the turn-angle as the transition occurs. This is unique behaviour among the rare-earths.

Gd₆₀Y₄₀ exhibits differing behaviour as the helimagnetic/ferromagnetic transition is approached. This transition occurs at low temperature, but is unusual in that an apparently frozen-in' state of coexisting ferromagnetism and helimagnetism sets in below -50 K. The nature of the phase boundary is discussed concerning this behaviour together with the possible role of random field effects.

Gd-Sc alloys of composition between 64% and 76.7% Gd were initially characterized over their full magnetically ordered temperature range by elastic constant measurements. Neutron diffraction was then used to make accurate structure determinations for the magnetic phases exhibited in this alloy system. Resistivity measurements have provided useful additional information regarding the phases, particularly with regard to the ferro-I phase observed in the alloy richest in Gd.

The magnetic phase diagram for the Gd-Sc system has been observed to be quite dissimilar to that of Gd-Y in the region of 70% Gd. First, there is a conical helix phase separating the helical and ferromagnetic phases, which is absent in Gd-Y. Secondly, the ferro-I phase of Gd-Y is considerably less extensive in Gd-Sc than in Gd-Y. This is unusual in view of earlier belief that this phase should be enhanced by the substitution of Sc for Y. Also, preliminary elastic constant and resistivity measurements for Gd₆₄Sc₃₆ have revealed rich and interesting behaviour in an applied magnetic field.

Item Type: Thesis (PhD)
Subjects: Q Science > QC Physics
Library of Congress Subject Headings (LCSH): Gadolinium compounds -- Magnetic properties, Yttrium compounds -- Magnetic properties, Scandium compounds -- Magnetic properties
Official Date: June 1989
Dates:
DateEvent
June 1989Submitted
Institution: University of Warwick
Theses Department: Department of Physics
Thesis Type: PhD
Publication Status: Unpublished
Supervisor(s)/Advisor: Palmer, Stuart B.
Format of File: pdf
Extent: 131 leaves : illustrations, charts
Language: eng

Request changes or add full text files to a record

Repository staff actions (login required)

View Item View Item

Downloads

Downloads per month over past year

View more statistics

twitter

Email us: wrap@warwick.ac.uk
Contact Details
About Us