ThMn12-type phases for magnets with low rare-earth content: Crystal-field analysis of the full magnetization process

Abstract

Rare-earth (R)-iron alloys are a backbone of permanent magnets. Recent increase in price of rare earths has pushed the industry to seek ways to reduce the R-content in the hard magnetic materials. For this reason strong magnets with the ThMn12 type of structure came into focus. Functional properties of R(Fe,T)12 (T-element stabilizes the structure) compounds or their interstitially modified derivatives, R(Fe,T)12-X (X is an atom of hydrogen or nitrogen) are determined by the crystal-electric-field (CEF) and exchange interaction (EI) parameters. We have calculated the parameters using high-field magnetization data. We choose the ferrimagnetic Tm-containing compounds, which are most sensitive to magnetic field and demonstrate that TmFe11Ti-H reaches the ferromagnetic state in the magnetic field of 52 T. Knowledge of exact CEF and EI parameters and their variation in the compounds modified by the interstitial atoms is a cornerstone of the quest for hard magnetic materials with low rare-earth content.

The Sm-Fe-V based 1:12 bulk magnets

“…This is going to result in phenomenal increase in demand for high performance permanent magnets (PMs), an industry which is already under pressure due to the high demand, high rare-earth (RE) prices and volatile supply chain of critical metals such as Dy, Tb. In an effort to reduce RE-metals consumption, there has been a renewed interest in 1:12 compounds with ThMn12-type crystal structure (space group I4/mmm) [1][2][3][4]. These compounds contain only a 7.7% of RE, compared with 11.8% in RE2Fe14B, and have a tetragonal structure, which is a requirement for uniaxial magnetocrystalline anisotropy (easy c-axis for RE=Sm and easy plane for RE=Nd).…”

Nanopowders of R2Fe14B-type compounds in high magnetic fields: The effects of substitutional and interstitial atoms on inter-sublattice exchange interaction

“…The magnetic behaviour of heavy R (or a mixture of heavy and light Rs) intermetallics with Fe is more interesting because various field-induced transitions can be expected in sufficiently external magnetic fields. The complete magnetization process ending with a field-induced ferromagnetic state often requires fields as high as tens or hundreds of Tesla [8].…”

Intrinsic magnetic properties of SmFe12−V alloys with reduced V-concentration

“…After the discovery of R 2 Fe 14 B (R=rare-earth) compounds with excellent magnetic properties, research and development in the field of permanent magnets has been focused almost exclusively on these alloys. However, in the last decade, because of the exponentially increasing demand for these magnets, increasing cost and supply risks involving the R-metals, there has been a renewed interest in the ThMn 12 -type (1:12) compounds [1,2,3,4]. These compounds contain only a 7.7% of R, compared with 11.8% in R 2 Fe 14 B, and they have a non-cubic structure (tetragonal), which is a requirement for uniaxial magnetocrystalline anisotropy (c-axis for R=Sm and easy plane for R=Nd).…”