Voltage-induced ferromagnetism in a diamagnet.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Voltage-controlled magnetism is crucial for low-power data processing and storage.
• Magnetoionic methods offer on/off control of ferromagnetism and magnetic anisotropy tuning.
• Existing methods tune known ferromagnets or induce magnetism from other magnetic states.

Purpose of the Study:

• To demonstrate voltage-induced ferromagnetism from a diamagnetic (zero-spin) state.
• To explore the electrical induction of magnetic phases in previously nonmagnetic materials.
• To investigate the underlying mechanisms of voltage-induced magnetism in FeS2.

Main Methods:

• Utilized ionic liquid-gated diamagnetic iron disulfide (FeS2) as a model system.
• Applied a low voltage (as little as 1 V) to induce electrostatic surface inversion.
• Performed anomalous Hall measurements to detect and quantify surface ferromagnetism.
• Employed density functional theory (DFT)-based modeling for theoretical explanation.

Main Results:

• Successfully induced a reversible insulator-metal transition in FeS2 with 1 V.
• Detected electrically tunable surface ferromagnetism at temperatures up to 25 K.
• DFT modeling confirmed Stoner ferromagnetism induced by filling of the eg band.

Conclusions:

• Ferromagnetism can be electrically induced from a diamagnetic state, expanding material possibilities.
• Ionic liquid gating provides a viable method for voltage-controlled magnetism in nonmagnetic materials.
• This work opens avenues for novel magnetic device applications using 'nonmagnetic' materials.