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

A series of gold clusters spanning the size range from Au6 through Au147 (with diameters from 0.7 to 1.7 nm) in icosahedral, octahedral, and cuboctahedral structure has been theoretically investigated by means of a scalar relativistic all-electron density functional method. One of the main objectives of this work was to analyze the convergence of cluster properties toward the corresponding bulk metal values and to compare the results obtained for the local density approximation (LDA) to those for a generalized gradient approximation (GGA) to the exchange-correlation functional. The average gold–gold distance in the clusters increases with their nuclearity and correlates essentially linearly with the average coordination number in the clusters. An extrapolation to the bulk coordination of 12 yields a gold–gold distance of 289 pm in LDA, very close to the experimental bulk value of 288 pm, while the extrapolated GGA gold–gold distance is 297 pm. The cluster cohesive energy varies linearly with the inverse o...

From clusters to bulk: A relativistic density functional investigation on a series of gold clusters Aun, n=6,…,147

Magnetic and crystallographic characteristics of rare-earth ternary carbides derived from R2Fe17 compounds

Thin films and quasi-two-dimensional systems show a wide range of ordering effects and related pattern-formation phenomena. The origins of these phenomena can often be traced to competition between the atomic (or molecular) interactions in the system and the resulting inherent frustration of the system. In magnetic thin films, a wide range of magnetic structures are possible as a result of the competition between the long-ranged dipolar interactions and localized interactions. This article reviews recent experimental and theoretical work which has developed our understanding of ordering and pattern formation in these films and in related structures.

Dipolar effects in magnetic thin films and quasi-two-dimensional systems

Hole concentration and T c in Bi 2 Sr 2 CaCu 2 O 8+δ

155Gd Mössbauer effect study of Gd2Fe17Nx

Magnetic properties of Gd2Fe17Cx

The 155 Gd Mossbauer effect and the magnetic properties of intermetallic compounds of the type Gd 2 Fe 17 C x were studied From the quadrupole splitting of the Mossbauer spectra we determined the signs and the magnitudes of the electric field gradients present at the gadolinium nuclei in these compounds The second-order field parameter A 2 0 estimated from these field gradients was shown to be in agreement with an easy magnetization direction parallel to the c axis, as found in Sm 2 Fe 17 C 06 

Effect of carbon take-up on the crystal-field effects in rare-earth compounds R2Fe17

155Gd Mössbauer measurements on the ceramic superconductor GdBa2Cu3O7

The 155Gd Mossbauer effect was studied in numerous intermetallic compounds of the type GdT2Si2 (T  Cr, Mn, Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Os, Ir, Au). From the quadrupole splitting of the Mossbauer spectra we determined the sign and magnitude of the electric field gradient present at the gadolinium nuclei in these compounds. The second-order field paramter A20 estimated from these field gradients was used to predict the easy magnetization directions for the various corresponding rare earth compounds RT2Si2. These predictions were found to be in satisfactory agreement with results of neutron diffraction data reported for several RT2Si2 in the literature.

M.W. Dirken

Papers

155Gd Mössbauer effect study of Gd2Fe17Nx

Magnetic properties of Gd2Fe17Cx

Effect of carbon take-up on the crystal-field effects in rare-earth compounds R2Fe17

155Gd Mössbauer measurements on the ceramic superconductor GdBa2Cu3O7

Crystal-field effects in rare earth compounds with the ThCr2Si2 structure