Effect of geometry on magnetization distortion in closed-circuit magnetic measurements

Chen, Christina; Higgins, A.

doi:10.1016/j.jmmm.2008.01.035

Cited by 11 publications

(9 citation statements)

References 17 publications

(26 reference statements)

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“…We have called this an apparent image effect, and have proposed an explanation based on localized saturation of the magnetic material of the electromagnet pole pieces resulting in a non-uniform field in the region around the sample [5]. This paper presents the results of computer modeling of the experiment, which confirms our explanation.…”

Section: Introductionsupporting

confidence: 73%

“…The samples were right circular cylinders of 1018 steel and Nd 2 Fe 14 B permanent magnet material of diameter D ¼ 12.56 mm and various lengths, giving L/D ratios of 0.23, 0.42, 0.47, 0.88, 1.2, and 1.8. Our previous experiments [5] showed that the apparent image effect is observed with soft as well as hard magnetic materials. Steel and NdFeB magnets were chosen as the sample materials because they have high saturation, and thus represent worst-case conditions for the appearance of the apparent image effect.…”

Section: Methodsmentioning

confidence: 88%

“…However, we have found and reported [4,5] that in permanent magnet samples with a small ratio of length to diameter, measured in a closed magnetic circuit, there is a marked drop in the measured magnetization in high applied fields. Fig.…”

Section: Introductionmentioning

confidence: 81%

“…1 is reproduced from Refs. [4,5] to illustrate the phenomenon. It depends on the magnitude of saturation magnetization and on length-to-diameter ratio, L/D, of the sample, and occurs for both soft magnetic materials and permanent magnets.…”

Section: Introductionmentioning

confidence: 99%

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Verification by finite element modeling for the origin of the apparent image effect in closed-circuit magnetic measurements

Chen

Graham

Pugh

et al. 2011

Journal of Magnetism and Magnetic Materials

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Section: Introductionsupporting

confidence: 73%

Section: Methodsmentioning

confidence: 88%

Section: Introductionmentioning

confidence: 81%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Verification by finite element modeling for the origin of the apparent image effect in closed-circuit magnetic measurements

Chen

Graham

Pugh

et al. 2011

Journal of Magnetism and Magnetic Materials

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“…This result is likely to be correlated to a smaller fraction of magnetic moments in Pt 60 Co 40 @CP-HMSNFs that are capable of being aligned parallel to the applied magnetic field because of the helical nanowire geometry. 35,36 Pt 60 Co 40 @CP-HMSNFs also exhibited smaller remanent magnetization, remanence ratio (saturation/remanent) and lower coercivity than Pt 60 Co 40 @MCM-41 did. Straight alloy nanowires are magnetically harder than helical nanowires, perhaps because of the stronger exchange interactions between the aligned magnetic domains in (and between) straight nanowires.…”

Section: Resultsmentioning

confidence: 92%

Functional helical silica nanofibers with coaxial mixed mesostructures for the fabrication of PtCo nanowires that display unique geometry-dependent magnetism

et al. 2015

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Helical mesoporous silicas are notable from a self-assembly and applications points of view. We report a novel confinement-free synthesis of chloropropyl-functionalized helical mesoporous silica nanofibers (CP-HMSNFs) possessing straight channels at the fiber center surrounded by concentric short-pitch helical channels. The chloropropyl groups are found mainly distributed at the central cylindrical portion of the fibers, allowing the selective inclusion of guest species to fabricate novel nanocomposite fibers. Moreover, the chloropropyl-functionalized nanofibers were applied as a hard template to fabricate helical platinum-cobalt (PtCo) alloy nanowires with small and narrowly distributed radii of gyration. The helical metal nanowires exhibited distinct ferromagnetic properties as compared with their straight counterpart. NPG Asia Materials (2015) 7, e181; doi:10.1038/am.2015.39; published online 22 May 2015 INTRODUCTIONHelical mesoporous silicas 1-11 are analogous to the self-assembled helical biomaterials in nature and have attracted a substantial amount of attention. These helical silicas are also promising hard templates for the preparation of helical nanowires composed of metals [12][13][14][15] or other compositions that may possess unique optical, 16,17 electromagnetic 9,18 or other properties. Efforts to understand the formation mechanism of these helical nanostructures provide additional insights into the interplay of the thermodynamics and kinetics of the assembly of structure-directing surfactants and inorganic silicate species 1,2,19,20 and may also lead to the design and synthesis of additional novel selfassembled nanomaterials with controllable mesostructures and morphologies, allowing for innovative applications. 9,11,21 The first synthesis of helical mesoporous silica materials displaying a MCM-41-like two-dimensional (2D)-hexagonal structure was performed in a static two-phase acidic system. 7 Helical 2D-hexagonal mesoporous silica nanofibers (HMSNFs) or nanorods were then synthesized in single-phase dilute solutions using chiral 5 or achiral 2,20,22 surfactants. The helical formation is mainly driven by a reduction in the free energy of the surface, from straight micellar rods until the free energy is balanced by an increased bending energy. 2,20 Alternatively, HMSNFs can be prepared by evaporation-induced selfassembly (EISA) in porous anodic alumina membranes. 23,24 The confined EISA may result in helical and other thermodynamically more stable mesophases, the former generally being kinetically favored. Notably, materials with mixed mesostructures can also be

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Apparent Image Effect in Closed-Circuit Magnetic Measurements

2008

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Magnetic measurements made under closed-circuit conditions are generally considered to be free from errors associated with the image effect. However, magnetic measurements on permanent magnet sample cylinders clamped between the pole pieces of an electromagnet show an apparent drop in magnetization with increasing applied field that is similar to the image effect found in open-circuit measurements. The closed-circuit effect has been measured for a range of sample geometries and materials, and occurs in both hard and soft magnetic materials. The drop in apparent magnetization is greater, and appears at lower fields, as the saturation magnetization of the sample increases. The effect increases as the length-to-diameter ratio of the sample decreases, and becomes minimal for 1 8. In addition to the apparent decrease in measured magnetization, there is a decrease in the measured magnetic field. We attribute the effect to a non-uniform magnetization of the electromagnet pole pieces, where local saturation distorts the magnetic flux distribution around the sample.Index Terms-Apparent image effect, closed-circuit magnetic measurement, distortions of magnetic field and magnetization.

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Effect of geometry on magnetization distortion in closed-circuit magnetic measurements

Cited by 11 publications

References 17 publications

Verification by finite element modeling for the origin of the apparent image effect in closed-circuit magnetic measurements

Verification by finite element modeling for the origin of the apparent image effect in closed-circuit magnetic measurements

Functional helical silica nanofibers with coaxial mixed mesostructures for the fabrication of PtCo nanowires that display unique geometry-dependent magnetism

Apparent Image Effect in Closed-Circuit Magnetic Measurements

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