Wydarzenia

Seminarium Międzynarodowego Laboratorium Silnych Pól Magnetycznych i Niskich Temperatur PAN

Nd-Fe-B-based permanent magnets: modern trends and used approaches

N.B. Kolchugina

Baikov Institute of Metallurgy and Materials Science, Russian Academy of Science, Moscow, Russia

20 years after discovery Nd-Fe-B-based permanent magnets the consistent increase in (BH)_max, which was related to improvements in the technology, such as the perfection of the texture (magnetization in a pulsed field), increase in the volume fraction of hard magnetic phase Nd₂Fe₁₄B, decrease in the oxygen content in the magnets, further reduce of grain size, improvement of magnetic isolation of each grain, i.e. the realization of ideal structure (Sagawa principles).

For the next 50 years, no composition, which can be an alternative for Nd-Fe-B alloys, will not be developed; nevertheless, the development of permanent magnets in this century will be profoundly different from that in the last century.

The modern trend in the development of high-coercivity magnets (for high-temperature applications) consists in the minimization of heavy rare-earth metal (REM) consumption, the use of which results in the decrease in magnetic energy product and substantial increase in the cost of magnets. The approach used in solving the problem is the precise engineering of grain-boundaries, namely, grain-boundary diffusion and grain-boundary structuring. This approach is realized in our studies by application of REM hydrides (high anisotropy-field layer method) and REM-rich alloying compositions (“two-alloy” method).

The use of the approach in designing the Nd-Fe-B permanent magnets for low-temperature applications is considered.

One more approach used in performing fundamental research in the Baikov Institute of Metallurgy and Materials Science consists in the application of high-purity rare-earth metals. The importance of application of high-purity metals is demonstrated by an example of heat-capacity measurements of distilled Er and Tm.