Magnetic Force Microscopy Studies of Magnetic Domain Structure in LaCoO3 and UMn2Ge2 PDF Download
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Author: Morgann Elizabeth Berg
Publisher:
ISBN:
Category :
Languages : en
Pages : 314
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Book Description
Magnetic force microscopy studies in varying temperature and applied external magnetic field of magnetic thin films of LaCoO3 under strain and single crystal UMn2Ge2 have been performed. In the case of LaCoO3 thin films the aim is an understanding of the response of the magnetic microstructure to different signs and degrees of strain and a further attempt to distinguish the effect of defects from strain-induced effects. In UMn2Ge2 the magnetic microstructure is imaged for the first time and signatures of a possible phase transition at 150 K and crystalline anisotropy are explored. The first portion of this dissertation focuses on the synthesis methods used to produce the samples investigated and the critical role of synthesis in producing high-quality samples. This is followed by a discussion of characterization techniques used to obtain local and global magnetic and structural characteristics, with particular emphasis on magnetic force microscopy including noise characteristics and a discussion of achieving a high force gradient sensitivity by optimizing the fiber-optic interferometer used for cantilever deflection detection. Design elements and features of the multi-mode variable-temperature atomic force microscope used to obtain magnetic force microscopy images are presented and results for LaCoO3 and UMn2Ge2 are discussed.
Author: Morgann Elizabeth Berg
Publisher:
ISBN:
Category :
Languages : en
Pages : 314
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Book Description
Magnetic force microscopy studies in varying temperature and applied external magnetic field of magnetic thin films of LaCoO3 under strain and single crystal UMn2Ge2 have been performed. In the case of LaCoO3 thin films the aim is an understanding of the response of the magnetic microstructure to different signs and degrees of strain and a further attempt to distinguish the effect of defects from strain-induced effects. In UMn2Ge2 the magnetic microstructure is imaged for the first time and signatures of a possible phase transition at 150 K and crystalline anisotropy are explored. The first portion of this dissertation focuses on the synthesis methods used to produce the samples investigated and the critical role of synthesis in producing high-quality samples. This is followed by a discussion of characterization techniques used to obtain local and global magnetic and structural characteristics, with particular emphasis on magnetic force microscopy including noise characteristics and a discussion of achieving a high force gradient sensitivity by optimizing the fiber-optic interferometer used for cantilever deflection detection. Design elements and features of the multi-mode variable-temperature atomic force microscope used to obtain magnetic force microscopy images are presented and results for LaCoO3 and UMn2Ge2 are discussed.
Author: Xinzhou Tan
Publisher:
ISBN:
Category :
Languages : en
Pages : 156
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Book Description
The first part of this dissertation introduces the theoretical background for the Magnetic Force Microscope (MFM), the Spin Polarized Scanning Tunneling Microscope (SP-STM), and the theoretical basis for magnetic domains.The second part addresses issues on the design and construction of a low temperature magnetic force microscope (LT-MFM) and its operation. The third part focuses on the LT-MFM experimental investigation on ternary UMn2Ge2 crystals. The forth part describes the construction and implementation of a low temperature SP-STM system. Scanning probe microscopy (SPM), beginning with the invention of the STM, was first developed to study the electronic properties of different materials, such as imaging high T[subscript c] superconductors. But soon, as the SPM family expanded, some of them developed into powerful techniques to characterize magnetic features. This category includes MFM and SP-STM. The former was widely used for imaging surface magnetic properties from hundreds of micrometers down to the nanometer scale, ideal for imaging magnetic domains. With our homemade LT-MFM system, we studied UMn2Ge2 single crystals, in which both the Uranium and Manganese atoms are magnetic. Flower-like magnetic domain pattern were found at room temperature, and they persisted all the way down to low temperature. Around 150K, Uranium atom ordering was revealed in the form of magnetic domain wall jumps, by partially saturating the sample and warming it up in zero field. In addition, the underlying mechanism of the flower pattern was explained using the domain branching scheme. On the other hand, a Low temperature SP-STM (LT-SP-STM) was designed and constructed, paving the way for spin mapping at the atomic scale thus characterizing magnetic materials with ultra-resolution.
Author: Elena Zueco
Publisher:
ISBN: 9783826566240
Category : Domain structures
Languages : en
Pages : 86
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Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
We present a magnetic force microscopy (MFM) analysis of arrays of submicron-scale Co dots fabricated by interference lithography. The dots are thin (180--300 Å) and elliptical in shape. MFM reveals that these structures relax into highly ordered remanent states whose symmetry and configuration are governed by their shape anisotropy. In particular, when the dots are saturated along their long-axis, a uniformly magnetized state persists at remanence. However, when the dots are saturated along their short-axis, they relax into a single-vortex state in which the circulation can have either sign. Both states are characterized by smoothly varying magnetization patterns and a high degree of uniformity across the array. We attribute the ordered behavior of these.structures to the film microstructure, which allows the shape anisotropy to dominate over magnetocrystalline anjsotropy. By imaging a series of minor-loop remanent states, we show that magnetization reversal in these structures occurs via the nucleation and annihilation of a single vortex. Magnetic hysteresis loop measurements are consistent with these observations and provide additional details. Furthermore, we present the results of micromagnetic simulations, which are in excellent agreement with both the MFM images and the hysteresis loop measurements. © 1998 Elsevier Science B.V. All rights reserved.
