Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1991. / Vita. Abstract. Includes bibliographical references (leaves 81-85). Also available via the Internet.

Magnetization processes in a sintered Nd-Fe-B permanent magnet (NEOMAX-35) were examined on a small scale using a Hall-effect microprobe with an active area 75 μm on a side. Probes were made by evaporating bismuth through a stencil mask onto glass slides. Experiments were performed by placing a probe onto the polished pole face of a Nd-Fe-B magnet and inserting the probe-magnet assembly into an electromagnet. Barkhausen steps, indicating rapid domain wall motion, were observed (superimposed upon the blank probe signal) in the demagnetization of a fully magnetized magnet. Magnetization traces for a thermally demagnetized Nd-Fe-B magnet did not exhibit measurable Barkhausen steps until a field of approximately 1.2 T was applied. The following observations were made for two thermally demagnetized samples which were cycled through minor hysteresis loops (maximum applied field of approximately 2 T): (1) virgin magnetization traces did not contain measurable Barkhausen steps, however all other forward and reverse magnetization traces did; (2) the initial reverse magnetization trace exhibited more and larger Barkhausen steps than subsequent traces; and (3) some Barkhausen steps were repeatable, that is, occurring at approximately the same field on each subsequent forward or reverse trace. Hall voltage signals were on the order of millivolts for probe currents of 10 mA.

No description available.

No description available.

Thesis (Ph.D.)--University of Western Australia, 2004.

No description available.

The magnetic properties of the (FexNi1-x)2B family of materials are explored using DFT calculations utilizing the FPLO and SPR-KKR code packages. It is found that a uniaxial magnetocrystalline anisotropy exists at around x = 0.8 with a magnetocrystalline anisotropy energy at around 0.3 MJ/m^3. A calculation of the lattice constant for these materials were attempted but failed due to the emergence of local minima and the calculations of magnetic properties were instead done using lattice parameters interpolated between known experimental values.

by Ku, Nim Chung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1997. / Includes bibliographical references. / by Ku, Nim Chung. / Acknowledgment --- p.i / Abstract --- p.ii / Table of contents --- p.iv / List of figures --- p.viii / List of tables --- p.xiv / Chapter Chapter One --- Introduction / Chapter 1.1 --- History of permanent magnet materials --- p.1 / Chapter 1.2 --- NdFeB intermetallic compound --- p.4 / References --- p.8 / Chapter Chapter Two --- Background / Chapter 2.1 --- Corrosion and corrosion control --- p.9 / Chapter 2.1.1 --- Electrochemical mechanisms --- p.10 / Chapter 2.1.2 --- Types of corrosion cell --- p.12 / Chapter 2.1.3 --- Types of corrosion --- p.14 / Chapter 2.1.4 --- Corrosion control --- p.15 / Chapter 2.2 --- Intermetallic compounds and phases --- p.19 / References --- p.26 / Chapter Chapter Three --- Instrumentation / Chapter 3.1 --- Introduction --- p.27 / Chapter 3.2 --- Vacuum evaporator --- p.28 / Chapter 3.3 --- Vacuum furnace --- p.29 / Chapter 3.4 --- Scanning electron microscopy (SEM) & Energy dispersive analysis (EDX) --- p.29 / Chapter 3.5 --- Corrosion chamber --- p.31 / Chapter 3.6 --- Vibrating sample magnetometer (VSM) --- p.31 / References --- p.43 / Chapter Chapter Four --- Moisture corrosion test on a bare NdFeB permanent magnet (without any coating) / Chapter 4.1 --- Introduction --- p.44 / Chapter 4.2 --- Experimental procedures --- p.45 / Chapter 4.3 --- Results from visual inspection --- p.45 / Chapter 4.4 --- Corrosion behavior --- p.46 / Chapter 4.5 --- Measurement of the saturated magnetization --- p.47 / Chapter 4.6 --- The effect of corrosion on the magnetic property of the NdFeB magnet --- p.48 / Chapter 4.7 --- Conclusions --- p.49 / References --- p.57 / Chapter Chapter Five --- Interfacial reaction between the A1 coating and the NdFeB magnet / Chapter 5.1 --- Introduction --- p.58 / Chapter 5.2 --- Experiments --- p.59 / Chapter 5.3 --- The Interaction between the A1 coating and Magnet --- p.60 / Chapter 5.4 --- Conclusions --- p.63 / References --- p.67 / Chapter Chapter Six --- Corrosion behavior of A1 coated NdFeB magnet in moist environment / Chapter 6.1 --- Introduction --- p.68 / Chapter 6.2 --- Experiments --- p.69 / Chapter 6.3 --- Results --- p.69 / Chapter 6.3.1 --- The annealed samples before corrosion test --- p.70 / Chapter 6.3.2 --- Microstructure changes after 3 days of corrosion --- p.70 / Chapter 6.3.3 --- Corrosion process in the annealed samples --- p.71 / Chapter 6.4 --- Corrosion behavior --- p.73 / Chapter 6.4.1 --- Effects of NaCl on the samples --- p.73 / Chapter 6.4.2 --- Effects of the inter-diffusion --- p.74 / Chapter 6.5 --- Conclusions --- p.75 / References --- p.79 / Chapter Chapter Seven --- Dual layer coating of either Ti/Al or Ni/Al on the NdFeB permanent magnet / Chapter 7.1 --- Introduction --- p.80 / Chapter 7.2 --- Experiments --- p.81 / Chapter 7.3 --- The Interaction between the A1 and Magnet --- p.81 / Chapter 7.3.1. --- The Ti/Al coated magnets --- p.82 / Chapter 7.3.2. --- The Ni/Al coated magnets --- p.83 / Chapter 7.4 --- Volume contraction of the intermetallic coatings --- p.84 / Chapter 7.5 --- Conclusions --- p.85 / References --- p.90 / Chapter Chapter Eight --- Conclusions and suggestions for further studies --- p.91

Due to the insecurity of the supply of raw materials needed for neodymium-iron-boron magnets, typically used in permanent magnet generators, the use of ferrite magnets as an alternative was investigated. The investigation was conducted by attempting to redesign a generator that previously used neodymium-iron-boron magnets for use with ferrite magnets. The major part of the redesign was to find an alternate rotor design with an electromagnetic design adapted to the characteristics of the ferrite magnets.It was found that  ferrite magnets can be used to replace neodymium-iron-boron magnets with changes to the electromagnetic design of the rotor. The changes of the electromagnetic design increase the amount of magnetically active material in the rotor and, therefore, require the mechanical design of the rotor to be changed. The new rotor design also requires some changes to the generator support structure. A design for a replacement rotor, using ferrite magnets, along with the required changes to the support structure, is presented.

Thesis (Ph. D.)--University of Missouri-Columbia, 1998. / Typescript. Vita. Includes bibliographical references (leaves 134-138). Also available on the Internet.