New Developments in Ferromagnetism ResearchFerromagnetism is a form of magnetism that can be acquired in an external magnetic field and usually retained in its absence, so that ferromagnetic materials are used to make permanent magnets. A ferromagnetic material may therefore be said to have a high magnetic permeability and susceptibility (which depends upon temperature). Examples are iron, cobalt, nickel, and their alloys. Ultimately, ferromagnetism is caused by spinning electrons in the atoms of the material, which act as tiny weak magnets. They align parallel to each other within small regions of the material to form domains, or areas of stronger magnetism. In an unmagnetised material, the domains are aligned at random so there is no overall magnetic effect. If a magnetic field is applied to that material, the domains align to point in the same direction, producing a strong overall magnetic effect. Permanent magnetism arises if the domains remain aligned after the external field is removed. Ferromagnetic materials exhibit hysteresis. In 2004, it was discovered that a certain allotrope of carbon, nanofoam, exhibited ferromagnetism. The effect dissipates after a few hours at room temperature, but lasts longer at cold temperatures. The material is also a semiconductor. It is thought that other similarly formed materials, of boron and nitrogen, may also be ferromagnetic. This new book rings together leading research from throughout the world. |
Contents
1 | |
Metallic Ferromagnetism in a Generalized Hubbard Model | 39 |
Electronic and Magnetic Properties of the Normal and Quaternary FullHeusler Alloys The Quest for New HalfMetallic Ferromagnets | 79 |
Ferromagnetic Domain Walls in Finite Systems MeanField Critical Exponents and Applications | 99 |
ParamagneticFerromagnetic Transition in a DoubleExchange Model | 119 |
The Classical Spectral Density Method at Work The Heisenberg Ferromagnet | 129 |
Spin Dependent Hot Electron Transport in Spin Valve Transistors Role of Hot Electron Spin Polarization and Schottky barrier | 185 |
Domain Structure in Ultrathin Ferromagnetic Films with Inclined Anisotropy | 209 |
Electric and Magnetic Properties in HiGHTc Ferromagnetism on GaMnN and Related DMS Materials | 231 |
287 | |
Common terms and phrases
alloys applied approximation assume atoms band behavior calculations classical compounds concentration condition conduction considered constant corresponding critical crystal curve density dependence described determined direction discussed distribution domain effect energy equation exchange interaction existence experimental expression external Fermi level ferromagnetic Figure film finite function Ga,Mn)N given graph Hamiltonian hence hot electron hysteresis loop important inclined anisotropy increase integral interaction ions layer leads magnetic field materials means measurements mechanism metals method observed obtained parallel paramagnetic parameters phase Phys Physics plane possible present problem properties quantum quantum mechanical reduced references region relation respectively sample saturation scattering Schottky barrier shown spectral spin dependent spin polarization spontaneous magnetization structure surface taking temperature theory transport units values various wave zero
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Page 1 - Science, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon Tong, Hong Kong SAR, People's Republic of China Received 3 June 1998, in final form 29 September 1998 Abstract.