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Caution to Apply Magnetic Barkhausen Noise Method to Nondestructive Evaluation of Plastic Deformation in Some ferromagnetic materials

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Chinese Journal of Mechanical Engineering 2019年第6期32卷 85-91页

作者： Manru He Takanori Matsumoto Tetsuya Uchimoto Toshiyuki Takagi Hongen Chen Shejuan Xie Zhenmao Chen Shannxi Engineering Research Center for NDT and Structural Integrity Evaluation State Key Laboratory for Strength and Vibration of Mechanical StructuresSchool of AerospaceXi’an Jiaotong UniversityXi’an 710049China Institute of Fluid Science Tohoku UniversitySendai 980‑8577Japan

Magnetic Barkhausen Noise(MBN) method is known as an effective nondestructive evaluation(NDE) method for evaluation of residual stress in ferromagnetic materials. Some studies on the feasibility of the MBN method for NDE of residual strains were also conducted and found applicable. However, these studies are mainly focused on the state of residual strains which were introduced through a one-cycle-loading process. In practice, however, structures may suffer from an unpredictable and complicated loading history, i.e., the final state of plastic strain may be induced by several times of large loads. Whether the loading history has influences on MBN signals or not is of great importance for the practical application of the MBN method. In this paper, several ferromagnetic specimens with the same final state of residual strain but of different loading history were fabricated and inspected by using a MBN testing system. The experimental results reveal that the loading history has a significant influence on the detected MBN signals especially for a residual strain in range less than 1%, which doubts the feasibility to apply the MBN method simply in the practical environment. In addition, micro-observations on the magnetic domain structures of the plastic damaged specimens were also carried out to clarify the influence mechanism of loading history on the MBN signals.

关键词： Plastic damage Deformation history MBN method ferromagnetic materials

Critical Behaviour of the One—Dimensional ferromagnetic t—J Model

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Chinese Physics Letters 2002年第1期19卷 108-110页

作者：杨赋王玉鹏 TechnicalInstituteofPhysics&Chemistry ChineseAcademyofSciencesBeijing100080 InstituteofPhysicsandCenterforCondensedMatterPhysics ChineseAcademyofSciencesBeijing100080

The one-dimensional super-symmetric ferromagnetic t-J model is studied via the thermal Bethe ansatz. Analytic expressions of the free energy for T→0 are obtained. A new critical behaviour beyond the universal class o... 详细信息

关键词： ferromagnetic materials

Effect of Barrier Width on Bias-Dependent Tunnelling in ferromagnetic Junctions

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Chinese Physics Letters 2004年第11期21卷 2271-2274页

作者：李飞飞肖明文李正中胡安许望 DepartmentofPhysics NanjingUniversityNanjing210093

We present a finite temperature theory for bias-dependent tunnelling in ferromagnetic tunnelling junctions. The effects of the barrier width d on the tunnelling magnetoresistance (TMR) and its sign change behaviour are discussed with this theory. Numerical results show that both the zero-bias TMR and the critical voltage Vc at which the TMR changes its sign decrease with the increasing barrier width for a considerably thick barrier junction. Furthermore, it is found that a minimum exists in the curve of Vc versus d if a composite junction is under oxidized.

关键词： ferromagnetic materials

Study on magnetic memory signals of medium carbon steel specimens with surface crack precut during loading process

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Rare Metals 2006年第Z1期25卷 431-435页

作者： DONG Lihong XU Binshi DONG Shiyun YE Minghui CHEN Qunzhi Basic Department Ordnance Engineering College Shijiazhuang 050003 China National Key Laboratory for Remanufacturing of Armored Force Engineering Institute Beijing 100072 China National Key Laboratory for Remanufacturing of Armored Force Engineering Institute Beijing 100072 China National Key Laboratory for Remanufacturing of Armored Force Engineering Institute Beijing 100072 China Basic Department Ordnance Engineering College Shijiazhuang 050003 China Beijing Aeronautical Technology Research Center Beijing 100076 China

Static tensile test and tensile-tensile fatigue test of medium carbon steel sheet specimens with surface crack precut were performed on MTS810 hydraulic testing machine to clear the meaning of the point of Hp(y) value zero. Magnetic memory signals were measured during the test process. The results show that only one point of Hp(y) zero value exists in all measured magnetic signal curves during the loading process, which should be a sign of intersection of positive-negative magnetic poles after magnetic ordered state appears and does not indicate the position of surface crack precut. The analysis shows that the surface crack precut can not interrupt the magnetic ordered state occurred during the test completely, hence its Hp(y) value is not zero. However, the crack extending to a penetrated defect at the instant of specimen′s fracture leads to the discontinuance of magnetic ordered state.

关键词： metal magnetic memory ferromagnetic materials surface crack precut Hp(y) zero value magnetic ordered state

An Anomalous Kerr Loop of LaBaMnO Thin Film

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Journal of materials Science & Technology 1998年第4期14卷 371-373页

作者： Hou, BH Xu, QL Ji, SZ Zhang, TP Peng, P Shang, CH Wang, YJ Xu, L Zhang, Y Univ Sci & Technol China Dept Phys Hefei 230026 Peoples R China Chinese Acad Sci Inst Phys State Key Lab Magnetism Beijing 100080 Peoples R China Chinese Acad Sci Inst Nucl Phys Shanghai 201800 Peoples R China

An anomalous Kerr loop was observed in an oriented LaBaMnO film annealed in oxygen. Many tiny crystal columns were observed with scanning tunneling microscope and magnetic force microscope. The magnetic moment m in the column is perpendicular outward to the surface, which forms a surface phase with spin pinning state. This spin pinning results in the obvious asymmetrical Kerr loop of magneto-optical effect when the magnetic field is in the two opposite directions vertical to the surface.

关键词： ferromagnetic materials

Oxygen vacancy control of electrical,optical,and magnetic properties of Fe_(0.05)Ti_(0.95)O_(2) epitaxial films

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Chinese Physics B 2021年第11期30卷 575-579页

作者： Qing-Tao Xia Zhao-Hui Li Le-Qing Zhang Feng-Ling Zhang Xiang-Kun Li Heng-Jun Liu Fang-Chao Gu Tao Zhang Qiang Li Qing-Hao Li College of Physics University-Industry Joint Center for Ocean Observation and Broadband CommunicationQingdao UniversityQingdao 266071China

High-quality Fe-doped TiO_(2) films are epitaxially grown on MgF_(2) substrates by pulsed laser *** x-ray diffraction and Raman spectra prove that they are of pure rutile ***-resolution transmission electron microscopy(TEM)further demonstrates that the epitaxial relationship between rutile-phased TiO_(2) and MgF_(2) substrates is 110 TiO_(2)||110 MgF_(2).The room temperature ferromagnetism is detected by alternative gradient *** increasing the ambient oxygen pressure,magnetization shows that it decreases monotonically while absorption edge shows a red *** transport property measurement demonstrates a strong correlation between magnetization and carrier *** influence of ambient oxygen pressure on magnetization can be well explained by a modified bound magnetization polarization model.

关键词： ferromagnetic materials semiconductors epitaxial films rutile TiO_(2)

Magneto-optical Kerr Effect in Co/Alq3 Granular Films

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Chinese Physics Letters 2009年第1期26卷 335-338页

作者：殷建芳倪刚吴俊奇袁明韵盛鹏王松有金庆原 Department of Optics Science and Engineering Fudan University Shanghai 200433 State Key Laboratory for Advanced Photonic materials and Devices Fudan University Shanghai 200433 Laboratory of Advanced materials Fudan University Shanghai 200433

A series of Co/Alq3 granular film samples are prepared using co-evaporating technique. The microstructures and magnetic properties are investigated. The Kerr spectra and optical constants of Cox（Alq3）1-x （0.19 ≤ x ≤ 1） granular films are measured using a magneto-optical Kerr spectrometer and a spectroscopic ellipsometer in the 1.5-4.5 eV photon energy range. The Kerr rotation reaches the maximum value of 0.5° in the x = 0.65 sample. The relationship between enhanced Kerr rotation and optical constants is discussed, and the concentration dependence of MOKE spectra is also investigated.

关键词： cobalt discontinuous metallic thin films ferromagnetic materials Kerr magneto-optical effect magnetic hysteresis

Very Regular Solutions for the Landau-Lifschitz Equation with Electric Current

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Chinese Annals of Mathematics,Series B 2018年第5期39卷 889-916页

作者： Gilles CARBOU Rida JIZZINI Laboratoire de Mathématiques Appliquées de Pau UMR CNRS 5142 Université de Pau et des Pays de l'Adour Institut de Mathématiques de Bordeaux UMR CNRS 5251 Université de Bordeaux 351 cours de la Libération

The authors consider a model of ferromagnetic material subject to an electric current, and prove the local in time existence of very regular solutions for this model in the scale of H^k spaces. In particular, they des... 详细信息

关键词： ferromagnetic materials Compatibility conditions Existence result

MAGNETOMECHANICAL BEHAVIORS OF GIANT MAGNETOSTRICTIVE materials

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Acta Mechanica Solida Sinica 2008年第1期21卷 15-18页

作者： Xu Gao Yongmao Pei Daining Fang Department of Engineering Mechanics Tsinghua University Beijing 100084 China School of Science Beijing Institute of Technology Beijing 100081 China

The Laves phase alloy Tb-Dy-Fe, commercially known as Terfenol-D, exhibits the giant room-temperature magnetostriction at moderate field strength of a few kOe due to its combination of high magnetostriction and low magnetocrystalline anisotropic energy. Thus, this pseudobinary rare earth iron compound has found quite a number of applications such as in magnetomechanical transducers, actuators and adaptive vibration control systems. The simultaneous measurements of magnetostriction and magnetization at various fixed compressive pre-stresses applied in the axial direction for Tb0.3Dy0.7Fe1.95 samples are presented. The results show that the magnetostriction increases with increasing compressive stress until it reaches 1742 ×10^6 under 25 MPa, so does the coercive magnetic field. And the hysteresis loop area for magnetization and magnetostriction also increases with the increment of applied compressive stresses. But the maximum magnetic susceptibility χ（dM/dH） is obtained under zero stress field and the strain derivative dλ/dH increases to the highest amplitude of 0.039×10^-6 A^-1m at a stress level of 5 MPa. In the strain versus magnetization intensity curve, the initial fiat stage mainly consisting of a 180° domain wall motion becomes shorter with increasing stress. It means more initial domains are driven to the transversal direction under the compressive stress before magnetization, which is consistent with the improvement of the magnetostriction.

关键词： magnetization magnetostriction ferromagnetic materials magnetomechanical coupling