Context : Recent experiments (2024) have confirmed the existence of a new magnetic phase “ Altermagnetism” , marking a paradigm shift in magnetic science beyond the traditional ferromagnetism and antiferromagnetism.
What is Altermagnetism?
- Ferromagnets: Parallel spin alignment with strong net magnetisation.
- Antiferromagnets: Alternating spins with zero net magnetisation.
- Altermagnets: Exhibit zero net magnetisation like antiferromagnets but possess spin-split electronic bands similar to ferromagnets.
- Caused by rotational or mirror symmetry in crystal structure, allowing spin-polarised currents without stray magnetic fields.
Key Properties
- Dual Magnetic Nature: Combine antiferromagnetic neutrality (no external magnetisation) with ferromagnetic spin splitting, enabling precise control of electron spins.
- Spin Polarisation: Exhibit spin polarisation in both real and momentum space, facilitating advanced spin-based functionalities.
- High Spin Splitting: Materials like Chromium Antimonide (CrSb) show energy differences up to 30× room temperature, enhancing spin control efficiency.
- No External Field: Despite internal magnetic ordering, altermagnets exhibit zero net magnetic moment, reducing interference in devices.
- Thermal Stability: Maintain magnetic behaviour at temperatures twice room temperature, ensuring industrial durability.
Chromium Antimonide (CrSb): A Promising Altermagnet
- Exceptional Spin Splitting: Displays record-high spin-splitting (~30× room temperature).
- Directional Conductivity: Shows Direction-Dependent Conduction Polarity (DDCP) n-type along layers, p-type across layers a first in known magnetism.
- High Crystal Purity: Single-crystalline structure ensures accurate measurement of anisotropic properties.
Applications
- Spintronics: Enables ultra-fast, low-energy, spin-based memory and data storage devices.
- Compact Electronics: Functions as both p-type and n-type material, simplifying circuit design and lowering production costs.
- Thermoelectrics: Enhances energy conversion efficiency for power systems.
- Simplified Manufacturing: Removes need for heterostructures or doping, promoting cost-effective fabrication.
- Sustainability: Composed of earth-abundant, non-toxic elements, ensuring eco-friendly technological development.
