MnBi₂ Is a Permanent Magnet

Area of Science:

• Materials Science
• Condensed Matter Physics
• Magnetism

Background:

• Understanding orbital angular momentum's impact on coercivity is crucial for developing new permanent magnets.
• High atomic number (Z) elements enhance spin-orbit coupling, a key factor in magnetic properties.
• The Mn-Bi system, containing the permanent magnet MnBi, is a promising platform for studying these relationships.

Purpose of the Study:

• To investigate the magnetic properties of the newly identified MnBi2 compound under high pressure.
• To elucidate the role of orbital angular momentum and spin-orbit coupling in MnBi2's magnetism.
• To explore the potential of high-Z elements in designing novel hard permanent magnets.

Main Methods:

• Synchrotron X-ray magnetic circular dichroism (XMCD) was employed to probe magnetism.
• Experiments were conducted at high pressure using a diamond anvil cell.
• First-principles calculations were used in conjunction with experimental data.

Main Results:

• MnBi2 exhibits ferromagnetic hysteresis at both 10 K and room temperature.
• Orbital angular momentum and spin-orbit coupling originating from Bi atoms were shown to induce magnetic anisotropy.
• Analysis of Bi p and d orbitals explained magnetic behavior variations within the Mn-Bi system.

Conclusions:

• The study confirms that high-Z elements, specifically bismuth, play a critical role in imparting magnetic anisotropy.
• The findings support the strategy of using high-Z elements in the synthesis of advanced permanent magnets.
• MnBi2 is a viable material for further investigation into high-pressure magnetic phenomena.