A review is given of the formation, the crystal structure and the magnetic properties of several classes of rare earth based intermetallic compounds that lend themselves as starting materials of permanent magnets. These compounds include R2Fe14B, R2Fe14C and R2Co14B and the large class of ternary rare earth compounds having the tetragonal ThMn12 structure. Special emphasis is given to the changes in magnetic properties of R2Fe17 compounds observed after interstitial solution of C or N atoms. The magnetic properties of all these compounds are discussed in terms of current models based on intersublattice and intrasublattice exchange and the interplay between the rare earth sublattice anisotropy and 3D sublattice anisotropy. A substantial portion of the review is devoted to manufacturing routes of permanent magnets and a description of the coercivity mechanisms operative in the magnets. A comparison is made of the performance and economic costs of various types of magnets and novel applications are briefly discussed.

https://iopscience.iop.org/article/10.1088/0034-4885/54/9/001/pdf

New developments in hard magnetic materials

The current and future status of rare earth permanent magnets

Publisher Summary This chapter reviews the synthesis techniques and the crystal chemistry of rare earth-transition metal-indides. It focuses on the phase relations and physical properties, and discusses the structure-property relationships. The crystal chemistry and chemical bonding of the R – T in compounds strongly depend on the composition. The rare earth metal-rich compounds exhibit typical intermetallic structures with relatively large coordination numbers, as found in close packed arrangements. The ternary rare earth metal-transition metal-indium systems contain a vast number of individual intermetallic compounds. The crystallographic data (lattice parameters) of all known indides is discussed in the chapter. The compounds are grouped with respect to the d element component. The chemical and various physical properties of rare earth-transition metal-indides are discussed in this chapter. Most of these indides are light gray in polycrystalline form. Single crystals have metallic luster. Although the rare earth metals are relatively electropositive elements similar to the alkaline earth metals, there is a significant difference in the stability of the ternary compounds.

Rare earth–transition metal–indides

Chapter 4 Magnetism and processing of permanent magnet materials

Crystal structure, magnetism and 57Fe Mössbauer spectra of ternary RE6Fe11Al3 and RE6Fe13Ge compounds

A new stable phase has been identified in the Nd-Fe-Si system. X-ray diffraction examination of single crystals was used to establish the crystal structure of Nd 6 Fe 13 Si. The tetragonal space group is I 4/ mcm and the lattice parameters are a = b = 0.8034(3)nm, c = 2.278(1)nm. The crystal structure is an ordered version of Nd 6 Ga 3 Fe 11 .Magnetic measurements show an antiferromagnetic behaviour.

A. Letant

Papers

A new phase in Nd2Fe14B magnets. Crystal structure and magnetic properties of Nd6Fe13Si

A New Phase in Nd2Fe14B Magnets. Crystal Structure and Magnetic Properties of Nd6Fe13Si.