Strain-Mediated Photomagnetic Effects in Heterostructured Nanoparticles of Prussian Blue Analogues

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Material Information

Title:
Strain-Mediated Photomagnetic Effects in Heterostructured Nanoparticles of Prussian Blue Analogues
Physical Description:
1 online resource (293 p.)
Language:
english
Creator:
Knowles, Elisabeth S
Publisher:
University of Florida
Place of Publication:
Gainesville, Fla.
Publication Date:

Thesis/Dissertation Information

Degree:
Doctorate ( Ph.D.)
Degree Grantor:
University of Florida
Degree Disciplines:
Physics
Committee Chair:
MEISEL,MARK W
Committee Co-Chair:
BISWAS,AMLAN
Committee Members:
HERSHFIELD,SELMAN PHILIP
LEE,YOONSEOK
TALHAM,DANIEL R

Subjects

Subjects / Keywords:
analogue -- blue -- core-shell -- ctist -- emr -- heterostructure -- magnetism -- molecular -- nanaoparticle -- pba -- photomagnetism -- ppim -- prussian -- strain
Physics -- Dissertations, Academic -- UF
Genre:
Physics thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract:
The photomagnetic properties of cubic heterostructured nanoparticles of Prussian blue analogues (PBAs) are reported for various morphologies (with length scales of 100 nm < l < 1 µm) studied over a wide range of temperature (2 K < T < 300 K) and magnetic field (µ0H < 10 T). These results focus on heterostructures of a pressure-sensitive NiCr-PBA (A) and a photomagnetic CoFe-PBA (B) to illuminate the strain effects that are induced in the nonphotoactive A component up to its ferromagnetic ordering temperature (Tc ~ 70 K). A charge-transfer induced spin-transition(CTIST) generates a lattice contraction in B during slow-cooling, and after irradiation with white light, the resulting stress is released by the photoinduced expansion of the B component at low temperatures (T < 150 K). The core of this work addresses the mechanism and extent of the strain in the A component of the heterostructures. With this goal, a series of BA core@shell nanoparticles with the same B cores and varying A shell thicknesses was investigated.In addition, the series of cubic nanoparticles allows a straightforward calculation of the high-field magnetization in the A shell. Thus, by employing the conjectured mechanisms of the decreased magnetism, the depth of the induced strain is extracted from the high-field data, revealing a strain depth of nominally 20 nm, which is a recurrent length  scale appearing for the PBAs. To accompany the high-field analysis, the seemingly simple step of numerically differentiating the low-field susceptibility data provides further elucidation of the strain effects. Specifically, these derivatives expose a sharpening of the A ordering temperature in the light state of the core@shell nanoparticles, an effect which is found to be ubiquitous for all of the A-containing heterostructures. This finding asserts the understanding that the photoinduced expansion of the B core relieves the stress that is applied to the A shell in the dark state. These core@shell studies were initially guided by prior core@shell@shell findings, which reveal that, while a free surface of A is not needed, a stress-sensitivity must be established by growing the A material on an underlying phase possessing even a subtly disparate framework. Finally, studies which sought to achieve photoeffects at more practical temperatures incorporated a CrCr-PBA (C) with a high-Tc (220 K) in novel BC, CB, andCAB heterostructures. To complement the bulk magnetism results, electron magnetic resonance (EMR) studies reveal that demagnetizing effects from domains, which have previously been observed in A films, play a central role in the photoinduced strain in the A shells of theBA particles. Moreover, while the EMR results confirm overall decreases in the high-field magnetism of the A component of the heterostructures, this investigation also unveils a history dependence of the photoeffect, where the system must be cycled through the ordering temperature of the B core to allow the A domains to fully relax. In addition to the studies of the heterostructured PBAs, the experimental techniques used in this work are briefly reviewed to lend understanding to the data from the various investigations. As part of this experimental effort, a novel optic sample rod for use in a commercial magnetometer was developed to increase the efficiency of irradiating the photoactive PBAs, as well as other intriguing photoactive systems. The design and construction of this sample rod is discussed in detail, and the vendors of the purchased components are given, along with the drawings and specifications of the custom-built pieces. Finally, thermal and optical characterizations of the new rod are presented and compared with the previous version to demonstrate the significantly improved efficiency.
General Note:
In the series University of Florida Digital Collections.
General Note:
Includes vita.
Bibliography:
Includes bibliographical references.
Source of Description:
Description based on online resource; title from PDF title page.
Source of Description:
This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility:
by Elisabeth S Knowles.
Thesis:
Thesis (Ph.D.)--University of Florida, 2013.
Local:
Adviser: MEISEL,MARK W.
Local:
Co-adviser: BISWAS,AMLAN.
Electronic Access:
RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2014-12-31

Record Information

Source Institution:
UFRGP
Rights Management:
Applicable rights reserved.
Classification:
lcc - LD1780 2013
System ID:
UFE0046071:00001