<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mo stretchy="false">(</mml:mo><mml:mi>Sm</mml:mi><mml:mo>,</mml:mo><mml:mi>Zr</mml:mi><mml:mo stretchy="false">)</mml:mo><mml:msub><mml:mi>Fe</mml:mi><mml:mrow><mml:mn>12</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub><mml:msub><mml:mi>M</mml:mi><mml:mi>x</mml:mi></mml:msub></mml:math>(<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mi>M</mml:mi><mml:mo>=</mml:mo><mml:mi>Zr</mml:mi><mml:mo>,</mml:mo><mml:mi>Ti</mml:mi><mml:mo>,</mml:mo><mml:mi>Co</mml:mi><mml:mo stretchy="false">)</mml:mo></mml:math>for Permanent-Magnet Applications:<i>Ab Initio</i>Material Design Integrated with Experimental Characterization
Munehisa Matsumoto, Takafumi Hawai, Kanta Ono
Abstract
In rare-earth permanent magnets (REPMs), trade-offs between intrinsic magnetic properties are often encountered. A recent example is ${\mathrm{Sm}\mathrm{Fe}}_{12}$ where excellent magnetic properties can be achieved at the sacrifice of bulk structure stability. Bulk structure stability is sustained by the presence of a third substitute element as is the case with ${\mathrm{Sm}\mathrm{Fe}}_{11}\mathrm{Ti}$, where $\mathrm{Ti}$ degrades magnetic properties. It is now in high demand to find out with which chemical composition a good compromise in the trade-off between structure stability and strong ferromagnetism is reached. We inspect the effects of representative substitute elements, $\mathrm{Zr}$, $\mathrm{Ti}$, and $\mathrm{Co}$ in ${\mathrm{Sm}\mathrm{Fe}}_{12}$ by combining ab initio data with experimental data from neutron diffraction. The trend in the intrinsic properties with respect to the concentration of substitute elements are monitored and a systematic way to search the best compromise is constructed. A certain minimum amount of $\mathrm{Ti}$ is identified with respect to the added amount of $\mathrm{Co}$ and $\mathrm{Zr}$. It is found that $\mathrm{Zr}$ brings about a positive effect on magnetization, in line with recent experimental developments, and we argue that this can be understood as an effective doping of extra electrons.