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Structural, magnetothermal, and magnetotransport properties of single crystal terbium silicon germanide and spontaneous generation of voltage in single crystal gadolinium silicon germanide and gadolinium.

紀錄類型:	書目-語言資料,印刷品 : Monograph/item
書名/作者:	Structural, magnetothermal, and magnetotransport properties of single crystal terbium silicon germanide and spontaneous generation of voltage in single crystal gadolinium silicon germanide and gadolinium.
作者:	Zou, Min.
面頁冊數:	132 p.
附註:	Source: Dissertation Abstracts International, Volume: 70-05, Section: B, page: 3128.
Contained By:	Dissertation Abstracts International70-05B.
標題:	Engineering, Materials Science.
ISBN:	9781109144536
摘要、提要註:	A systematic study of single crystalline Tb5Si2.2Ge1.8, including magnetic field induced crystallographic and magnetic phase transformations, magnetocaloric effect, ferromagnetic short-range correlations, electrical resistivity, magnetoresistance, and spontaneous generation of voltage (SGV) has been presented. A study of SGV in single crystalline Gd5Si2Ge2 and Gd has also been included.
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3355553

Structural, magnetothermal, and magnetotransport properties of single crystal terbium silicon germanide and spontaneous generation of voltage in single crystal gadolinium silicon germanide and gadolinium.
Zou, Min.

Structural, magnetothermal, and magnetotransport properties of single crystal terbium silicon germanide and spontaneous generation of voltage in single crystal gadolinium silicon germanide and gadolinium. - 132 p.

Source: Dissertation Abstracts International, Volume: 70-05, Section: B, page: 3128.

Thesis (Ph.D.)--Iowa State University, 2009.

A systematic study of single crystalline Tb5Si2.2Ge1.8, including magnetic field induced crystallographic and magnetic phase transformations, magnetocaloric effect, ferromagnetic short-range correlations, electrical resistivity, magnetoresistance, and spontaneous generation of voltage (SGV) has been presented. A study of SGV in single crystalline Gd5Si2Ge2 and Gd has also been included.

ISBN: 9781109144536Subjects--Topical Terms:

422974
Engineering, Materials Science.

Structural, magnetothermal, and magnetotransport properties of single crystal terbium silicon germanide and spontaneous generation of voltage in single crystal gadolinium silicon germanide and gadolinium.
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035 $a (UMI)AAI3355553
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100 1 $a Zou, Min. $3 423028
245 1 0 $a Structural, magnetothermal, and magnetotransport properties of single crystal terbium silicon germanide and spontaneous generation of voltage in single crystal gadolinium silicon germanide and gadolinium.
300 $a 132 p.
500 $a Source: Dissertation Abstracts International, Volume: 70-05, Section: B, page: 3128.
500 $a Advisers: Vitalij K. Pecharsky; Karl A. Gschneidner, Jr.
502 $a Thesis (Ph.D.)--Iowa State University, 2009.
520 $a A systematic study of single crystalline Tb5Si2.2Ge1.8, including magnetic field induced crystallographic and magnetic phase transformations, magnetocaloric effect, ferromagnetic short-range correlations, electrical resistivity, magnetoresistance, and spontaneous generation of voltage (SGV) has been presented. A study of SGV in single crystalline Gd5Si2Ge2 and Gd has also been included.
520 $a The metamagnetic-like transitions and giant magnetocaloric effect were observed with the magnetic field applied parallel to the a- and c-axes, but not the b-axis in a Tb5Si 2.2Ge1.8 single crystal. The in-situ x-ray powder diffraction study indicates that these metamagnetic-like transitions are coupled to a crystallographic phase transformation occurring via strong magnetoelastic interactions. The magnetocrystalline anisotropy plays an important role in this system. Magnetic fields less than 40 kOe can not drive either the magnetic or the crystallographic phase transition to completion for Tb5Si2.2Ge1.8 powder due to the strong single ion anisotropy of Tb.
520 $a Magnetic field dependencies of the critical temperatures of magnetic phase transitions of Tb5Si2.2Ge1.8 are highly anisotropic for both the main magnetic ordering process occurring around 120 K and a spin reorientation transition at ~70 K. Magnetic-field-induced phase transitions occur with the magnetic field applied isothermally along the a-and b-axes (but not along the c-axis) between 1.8 and 70 K in fields below 70 kOe. Strongly anisotropic thermal irreversibility is observed in the Griffiths phase regime between 120 and 200 K with applied fields ranging from 10 to 1000 Oe. Our data: (1) show that the magnetic and structural phase transitions around 120 K are narrowly decoupled; (2) uncover the anisotropy of ferromagnetic short-range order in the Griffiths phase; and (3) reveal some unusual magnetic domain effects in the long-range ordered state of the Tb5Si2.2Ge1.8 compound. The temperature-magnetic field phase diagrams with field applied along the three major crystallographic directions have been constructed.
520 $a The positive colossal magnetoresistance (CMR) with a magnitude of ~150% was observed with the magnetic field applied parallel to the a-axis, but not the b- and c-axes in Tb5Si 2.2Ge1.8 single crystals. The electrical resistivity shows a low-temperature high-resistivity behavior (i.e. the resistivity at low temperature is higher after the transformation to the low temperature phase than the resistivity of the phase before the transition) along the a-axis, contrary to those along the b- and c-axes. The positive CMR effect originates from an intrinsic crystallographic phase coexistence state frozen below the Curie Temperature (TC). The differences in the temperature dependencies of electrical resistivities and longitudinal magnetoresistance along the a-axis and those along the b- and c-axes can be explained by the geometry of the phase boundaries at low temperatures, and the inability of the external magnetic field to induce the crystallographic phase transformation along the b- and c-axes.
520 $a Temperature-induced SGVs were observed along all three principal crystallographic axes of Tb5Si2.2Ge1.8, but not in Gd. Field-induced SGVs were observed with magnetic fields less than 40 kOe applied along the a-axis of Tb5Si2.2Ge1.8, and the c-axis of Gd. The absence of the temperature induced SGV in Gd indicates the key role first-order phase transformations play in the appearance of the effect when temperature varies. The anisotropy of magnetic field induced SGV in Tb5Si2.2Ge1.8 and the existence of field induced SGV in Gd, highlight the importance of the magnetocaloric effect in bringing about the SGV. In single crystal and polycrystalline Gd5Si 2Ge2 during the coupled magneto-structural transformations, reversible and repeatable SGV responses of the materials to the temperature and magnetic field have been observed. The parameters of the response and the magnitude of the signal are anisotropic and rate dependent. The magnitude of the SGV signal, and the critical temperatures and critical magnetic fields at which the SGV occurs vary with the rate of temperature and magnetic field changes.
590 $a School code: 0097.
650 4 $a Engineering, Materials Science. $3 422974
690 $a 0794
710 2 $a Iowa State University. $b Materials Science and Engineering. $3 423029
773 0 $t Dissertation Abstracts International $g 70-05B.
790 1 0 $a Pecharsky, Vitalij K., $e advisor
790 1 0 $a Gschneidner, Karl A., Jr., $e advisor
790 1 0 $a Tan, Xiaoli $e committee member
790 1 0 $a Canfield, Paul $e committee member
790 1 0 $a Schmalian, Joerg $e committee member
790 $a 0097
791 $a Ph.D.
792 $a 2009
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3355553