Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.680511
Title: High magnetic moment materials for thin-film applications at cryogenic temperatures
Author: Scheunert, G.
ISNI:       0000 0004 5915 9067
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2014
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Abstract:
The possibility of using heavy rare earth metals and some of their alloys as pole piece materials for nanoscale electromagnets as in magnetic recording devices (hard drive disks) at cryogenic temperatures was evaluated. To set the frame an extensive literature review on high-moment materials and concepts is presented. Thin films of Permendur (Fe6%Co35 alloys), gadolinium (Gd), dysprosium (Dy), Dy50Gd50 binary alloys, terbium (Tb), holmium (Ho), DyRh binary alloys, and DyRhX (X = Fe, Ni, Co, Gd) ternary alloys were magnetron-sputtered and characterised for their chemical and crystal structure. In-plane magnetic properties were investigated over a temperature range of T = 3 -300 K by SQUID magnetometry, with an emphasis on the saturation magnetisation, i.e. the magnetic moment per unit volume, and points of magnetic transition such as Curie temperature. All heavy rare earth metals (Gd, Dy, DyGd, Tb, Ho) were found to be suitable write-pole candidates, for their saturation magnetisation exceeds that of Fe65Co35 in the cryogenic temperature regime. In terms of reasonably high magnetisation at moderate temperatures, DyGd and Tb are deemed the best materials. However, other write-pole relevant magnetic properties such as softness and initial permeability were unfavourable for all heavy rare earth metals. The DyRh binary and DyRhX ternary alloy system were found to be completely unsuitable, since they had very low saturation magnetisation, due to antiparallel coupling of the rare earth and the transition metals, as well as very low Curie points, i.e. operating temperatures of T -0 K. All thin films had saturation magnetisations slightly reduced, and transition temperatures slightly lower, than that of their bulk counterparts as a result of finite size effects.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.680511  DOI: Not available
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