Magnetism is an old and well-researched topic, lending itself to many applications, like motors and transformers. However, new magnetic materials and phenomena are being studied and discovered, one of which is altermagnets.
Altermagnets exhibit a unique blend of magnetic characteristics, setting them apart from conventional magnetic materials like ferromagnets and antiferromagnets. These materials exhibit properties observed in both ferromagnets and antiferromagnets, making their study enticing.
The current research, published in Physical Review Letters, explores the thermal properties of altermagnets and was led by Prof. Wanxiang Feng and Prof. Yugui Yao from the Beijing Institute of Technology.
Speaking of their motivation behind exploring altermagnets, Prof. Feng told Phys.org, "Magnetism is an ancient and fascinating topic in solid-state physics. While exploring non-collinear magnets over the past decades, we encountered a new type of collinear magnet, the altermagnet."
Prof. Yao added, "With a dual nature resembling both ferromagnets and antiferromagnets, altermagnets intrigued us with the potential for novel physical effects. Our motivation stemmed from the desire to understand and unlock the unique properties of these magnetic materials."
The emergence of magnetism
Magnetic properties emerge from the behavior of atoms, particularly the arrangement and movement of electrons within a material.
"In magnetic materials, due to the exchange interaction between atoms, the spin magnetic moments arrange parallel or antiparallel, forming the most common ferromagnets and antiferromagnets, respectively, which have been studied for over a century," explained Prof. Feng.
Altermagnets defy conventional norms by embodying a dual nature—resembling antiferromagnets with zero net magnetization and ferromagnets with non-relativistic spin splitting.
In altermagnets, collinear antiparallel magnetic order combines with non-relativistic spin splitting, resulting in zero net magnetization akin to antiferromagnets and ferromagnetic spin dynamics simultaneously.
This unique behavior emerges from the intricate interplay of atoms within the crystal structure. For instance, ruthenium dioxide, the subject of this research, showcases spin degeneracy induced by nonmagnetic oxygen atoms, breaking spatial and time symmetries. This leads to the unique magnetic properties of the material.
Additionally, altermagnets exhibit a unique spin polarization. The term "spin polarization" means that a preponderance of electron spins tends to align in a particular direction.
The spin polarization is noteworthy in altermagnets because it occurs in the physical arrangement of atoms (real space) and in the momentum space, where the distribution of electron spins in the material is considered.
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