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Domain structure investigations in m...

Venkateswaran, Sai Prasanth.

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Domain structure investigations in multiferroic Heusler ferromagnetic shape memory alloys.

Record Type:	Language materials, printed : Monograph/item
Title/Author:	Domain structure investigations in multiferroic Heusler ferromagnetic shape memory alloys./
Author:	Venkateswaran, Sai Prasanth.
Description:	176 p.
Notes:	Adviser: Marc De Graef.
Contained By:	Dissertation Abstracts International68-01B.
Subject:	Engineering, Materials Science. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3248505

Domain structure investigations in multiferroic Heusler ferromagnetic shape memory alloys.
Venkateswaran, Sai Prasanth.

Domain structure investigations in multiferroic Heusler ferromagnetic shape memory alloys. - 176 p.

Adviser: Marc De Graef.

Thesis (Ph.D.)--Carnegie Mellon University, 2007.

Multiferroic ferromagnetic shape memory alloys form an interesting subset of functional materials that exhibit two ferroic properties, ferromagnetism and ferroelasticity, in the same phase. They exhibit a spontaneous magnetization as a result of a ferromagnetic transformation (paramagnetic → ferromagnetic) and a spontaneous deformation as a result of a ferroelastic martensitic transformation (austenite → martensite), both of which can be reoriented by their respective magnetic and stress fields. The resulting high strains are a consequence of mobile magnetic boundaries and structural boundaries associated with the ferroic transformations. While these materials are promising for high strain applications, a microscopic study of their magnetic and structural boundaries is still lacking.Subjects--Topical Terms:

1017759
Engineering, Materials Science.

Domain structure investigations in multiferroic Heusler ferromagnetic shape memory alloys.
LDR:03426nam 2200313 a 45 001 970694
005 20110921
008 110921s2007 eng d
035 $a (UMI)AAI3248505
035 $a AAI3248505
040 $a UMI $c UMI
100 1 $a Venkateswaran, Sai Prasanth. $3 1294730
245 1 0 $a Domain structure investigations in multiferroic Heusler ferromagnetic shape memory alloys.
300 $a 176 p.
500 $a Adviser: Marc De Graef.
500 $a Source: Dissertation Abstracts International, Volume: 68-01, Section: B, page: 0564.
502 $a Thesis (Ph.D.)--Carnegie Mellon University, 2007.
520 $a Multiferroic ferromagnetic shape memory alloys form an interesting subset of functional materials that exhibit two ferroic properties, ferromagnetism and ferroelasticity, in the same phase. They exhibit a spontaneous magnetization as a result of a ferromagnetic transformation (paramagnetic → ferromagnetic) and a spontaneous deformation as a result of a ferroelastic martensitic transformation (austenite → martensite), both of which can be reoriented by their respective magnetic and stress fields. The resulting high strains are a consequence of mobile magnetic boundaries and structural boundaries associated with the ferroic transformations. While these materials are promising for high strain applications, a microscopic study of their magnetic and structural boundaries is still lacking.
520 $a This thesis focuses on the interplay between the microstructure and the magnetic structure in Heusler ferromagnetic shape memory alloys (FSMA), especially Ni2MnGa, the alloy that has gained significant scientific and technological interest. The FSMA Ni2MnGa undergoes an atomic ordering transformation to a Heusler structure prior to the ferroic transformations. A systematic investigation of the atomic ordering defects (antiphase boundaries) was performed, which was then followed by the study of their interaction with the ensuing magnetic domain walls and structural twin boundaries. Transmission electron microscopy was used as the main experimental technique to characterize the antiphase boundaries, magnetic domain walls and twin boundaries.
520 $a The experimental work in this thesis clearly demonstrates a strong interaction between the microstructural antiphase boundaries and the magnetic domains of the atomically ordered Heusler phase (austenite). The change in antiphase boundary density upon high temperature annealing was correlated to the change in magnetic properties (coercivity) of the alloy. The antiphase boundaries act as strong pinning sites for the magnetic domain walls in both austenite and martensite.
520 $a The evolution of the different structures observed by in-situ dynamic experiments throws light on the effect of antiphase boundaries on the ferroic transformations. The magnetic domain structure of the Heusler phase exhibits complete domain memory across the magnetic and structural martensitic transformation, a phenomenon hitherto unknown. The ability to tailor the different structures by heat treatment provides us a methodology to tune the alloy properties.
590 $a School code: 0041.
650 4 $a Engineering, Materials Science. $3 1017759
650 4 $a Engineering, Metallurgy. $3 1023648
650 4 $a Physics, Condensed Matter. $3 1018743
690 $a 0611
690 $a 0743
690 $a 0794
710 2 0 $a Carnegie Mellon University. $3 1018096
773 0 $t Dissertation Abstracts International $g 68-01B.
790 $a 0041
790 1 0 $a De Graef, Marc, $e advisor
791 $a Ph.D.
792 $a 2007
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3248505