Magnetocrystalline anisotropy of Fe3B, Fe2B and Fe1.4Co0.6B as studied by Lorentz electron microscopy, singular point detection and magnetization measurements

1991 ◽  
Vol 96 (1-3) ◽  
pp. 189-196 ◽  
Author(s):  
W. Coene ◽  
F. Hakkens ◽  
R. Coehoorn ◽  
D.B. de Mooij ◽  
C. de Waard ◽  
...  
2000 ◽  
Vol 15 (11) ◽  
pp. 2488-2493 ◽  
Author(s):  
A. N. Thorpe ◽  
F. E. Senftle ◽  
M. Holt ◽  
J. Grant ◽  
W. Lowe ◽  
...  

Magnetization measurements, transmission electron microscopy (TEM), and high-resolution micro-x-ray fluorescence (μ-XRF) using a synchrotron radiation source (Advanced Photon Source) were used to examine Fe3O4 particle agglomerates of nominally 10-nm particles at low concentrations (down to 0.03%) in thick epoxy resin samples. The magnetization measurements showed that at low concentrations (<0.5%) the magnetite particles, although closely packed in the agglomerates, did not interact magnetically. Predicated on a 2-μm sample step scan, the μ-XRF results were compatible with the presence of spherical agglomerates due to magnetostatic attraction, and these ranged in size from 100 to several thousand nanometers, as observed in TEM measurements. At smaller step scans the resolution could be significantly improved. Thus, the synchroton μ-XRF method was very useful in detecting very small concentrations of particles in thick samples and could probably be used to detect particles in amounts as low as 10−16 g.


Physica B+C ◽  
1977 ◽  
Vol 86-88 ◽  
pp. 210-212 ◽  
Author(s):  
R. Gröβinger ◽  
W. Steiner ◽  
F. Culetto ◽  
H. Kirchmayr

1993 ◽  
Vol 313 ◽  
Author(s):  
Mary Beth Stearns ◽  
Yuanda Cheng

ABSTRACTSeveral series of CoxAg1-x granular thin films (-3000Å) were fabricated by coevapora-tion of Co and Ag in a dual e-beam UHV deposition system at varying substrate temperatures. These films have low field magnetoresistance values as large as 31% at room temperature and 65% at liquid N2 temperature. The structure of the films was determined using magnetization measurements as well as x-ray and various electron microscopy techniques. The composition was determined using Rutherford backscattering spectroscopy. The Magnetoresistance was measured at both room and liquid N2 temperatures.We deduce from the magnetization and RBS Measurements that the films consist of Co globules embedded in a Ag Matrix and that there is no appreciable mixing of the Co and Ag atoms in the films deposited at substrate temperatures ≥ 400°K. The size of the Co globules is seen to increase with increasing Co concentration and the maximum magnetoresistance occurs in those films having the smallest Ag thickness which provides magnetic isolation of the Co globules.We suggest that the large magnetoresistance of these films arises from the same mechanism which causes the low field magnetoresistance in pure ferromagnets, namely, the scattering of the highly polarized d conduction electrons of the Co at magnetic boundaries. The large increase in the room temperature magnetoresistance of the CO/Ag films as compared to those of pure 3d ferromagnetic films is due to the distance between the magnetic boundaries being reduced to a few nanometers, because of the small size of the single domain Co globules, as compared to a few microns in 3d ferromagnets.


2022 ◽  
Vol 19 (1) ◽  
pp. 707-737
Author(s):  
Xueyi Ye ◽  
◽  
Yuzhong Shen ◽  
Maosheng Zeng ◽  
Yirui Liu ◽  
...  

<abstract> <p>Singular point detection is a primary step in fingerprint recognition, especially for fingerprint alignment and classification. But in present there are still some problems and challenges such as more false-positive singular points or inaccurate reference point localization. This paper proposes an accurate core point localization method based on spatial domain features of fingerprint images from a completely different viewpoint to improve the fingerprint core point displacement problem of singular point detection. The method first defines new fingerprint features, called furcation and confluence, to represent specific ridge/valley distribution in a core point area, and uses them to extract the innermost Curve of ridges. The summit of this Curve is regarded as the localization result. Furthermore, an approach for removing false Furcation and Confluence based on their correlations is developed to enhance the method robustness. Experimental results show that the proposed method achieves satisfactory core localization accuracy in a large number of samples.</p> </abstract>


2020 ◽  
Vol 10 (11) ◽  
pp. 3868
Author(s):  
Jiong Chen ◽  
Heng Zhao ◽  
Zhicheng Cao ◽  
Fei Guo ◽  
Liaojun Pang

As one of the most important and obvious global features for fingerprints, the singular point plays an essential role in fingerprint registration and fingerprint classification. To date, the singular point detection methods in the literature can be generally divided into two categories: methods based on traditional digital image processing and those on deep learning. Generally speaking, the former requires a high-precision fingerprint orientation field for singular point detection, while the latter just needs the original fingerprint image without preprocessing. Unfortunately, detection rates of these existing methods, either of the two categories above, are still unsatisfactory, especially for the low-quality fingerprint. Therefore, regarding singular point detection as a semantic segmentation of the small singular point area completely and directly, we propose a new customized convolutional neural network called SinNet for segmenting the accurate singular point area, followed by a simple and fast post-processing to locate the singular points quickly. The performance evaluation conducted on the publicly Singular Points Detection Competition 2010 (SPD2010) dataset confirms that the proposed method works best from the perspective of overall indexes. Especially, compared with the state-of-art algorithms, our proposal achieves an increase of 10% in the percentage of correctly detected fingerprints and more than 16% in the core detection rate.


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