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Elements Of X Ray Diffraction

Understanding the correlation between magnetic properties and nanostructure involves collaborative efforts between chemists, physicists, and materials scientists to study both fundamental properties and potential applications. This article introduces a classification of nanostructure morphology according to the mechanism responsible for the magnetic properties. The fundamental magnetic properties of interest and the theoretical frameworks developed to model these properties are summarized. Common chemical and physical techniques for the fabrication of magnetic nanostructures are surveyed, followed by some examples of recent investigations of magnetic systems with structure on the nanometer scale. The article concludes with a brief discussion of some promising experimental techniques in synthesis and measurements.

Magnetic Properties of Nanostructured Materials

TOPICAL REVIEW: Nanomagnetics

Size dependence of nanostructures: Impact of bond order deficiency

New nanocrystalline high-remanence Nd-Fe-B alloys by rapid solidification

Enhanced magnetic properties in rapidly solidified Nd-Fe-B based alloys

Microstructure analysis of nanocrystalline Fe-Nd-B ribbons with enhanced hard magnetic properties

The effect of grain size on the magnetic properties of a rapidly solidified low boron Fe‐Nd‐B alloy, both in directly quenched and in the overquenched and annealed conditions, has been studied. The magnetic properties in the as‐quenched crystalline state and changes occurring on annealing of the overquenched ribbons are discussed in relation to the microstructure. High values of the remanent magnetization, above 0.9 T (9 kG), in combination with coercivities of 1100 kA m−1 (13.7 kOe), have been observed for the directly quenched, isotropic single‐phase ribbons, for certain combinations of process conditions. The mean‐grain size for these ribbons measured on the roll contact side was found in some cases to be <20 nm, representing an essentially nanocrystalline structure. The enhanced remanence is considered to result from intergranular magnetic exchange interactions between fine adjacent grains. The overquenched ribbons were aged at temperatures between 500 and 800 °C for various times and these exhibited ...

Effect of grain size and microstructure on magnetic properties of rapidly solidified Fe82.4Nd13.1B4.5 alloy

The effects of a nanocrystalline structure on the magnetic properties of isotropic melt spun Fe-Nd-B alloy ribbon are discussed. Three classes of alloys are considered: (a) low Nd (8-10 at.%) which also contains alpha -Fe; (b) near-stoichiometric Nd contents (11-13 at.%) which are single phase Fe/sub 14/Nd/sub 2/B; (c) high Nd (16-20 at.%) which also contains a Nd-rich phase. For types (a) and (b), as the scale of the nanostructive decreases, the remanence J/sub r/ is increasingly above J/sub s//2, while the coercivity H/sub cj/ is decreased, with a linear J/sub r/-H/sub cj/ relationship. No J/sub r/ enhancement occurs for type (c) alloys, even for a nanocrystalline structure, but rather a decrease due to volume dilution of the Fe/sub 14/Nd/sub 2/B phase. These effects are discussed in terms of inter-grain exchange coupling and decoupling, and the implications with respect to permanent magnets with improved properties are considered. It is demonstrated that the benefits of enhanced J/sub r/ in terms of improved energy product are limited by corresponding attenuation of the coercivity. >

Azwar Manaf

Papers

New nanocrystalline high-remanence Nd-Fe-B alloys by rapid solidification

Enhanced magnetic properties in rapidly solidified Nd-Fe-B based alloys

Microstructure analysis of nanocrystalline Fe-Nd-B ribbons with enhanced hard magnetic properties

Effect of grain size and microstructure on magnetic properties of rapidly solidified Fe82.4Nd13.1B4.5 alloy

Magnetic properties and microstructural characterisation of isotropic nanocrystalline Fe-Nd-B based alloys