In a paper published in the Journal of Materials Chemistry C we have studied a new type of magnetism - altermagnetism. This phenomenon, which was predicted only a few years ago, is capable of revolutionizing the electronics of the future. Altermagnetics combine the properties of both ferromagnetics (spin degeneracy) and antiferromagnetics, exhibiting zero total magnetic moment. This makes them ideal candidates for spintronics, a technology where information is encoded not by charge but by the spin of particles, which will make it possible to create energy-independent devices at the nanoscale.
The focus of the new research is on ultrathin GdAlSi (gadolinium-aluminum-silicon) metal films, which approach the thickness of several layers. Using computer simulations, we have studied how the material's altermagnetic properties evolve in the transition from bulk crystals to nanometer layers. It turned out that the key feature of altermagnetism - the direction-dependent spin-dependent splitting of electronic states - is preserved even in films a couple of nanometers thick. This splitting arises from the special symmetry of the crystal, where the magnetic moments on gadolinium atoms alternate in strict order between layers while preserving rotational symmetry and translation. For example, at certain points of the Brillouin zone, the electron spins abruptly change direction - as if the compass arrow suddenly flips.
However, when the film thickness is reduced to one unit cell, the effects characteristic of the bulk material begin to weaken. The reason is the influence of the surface: atoms at the edges of the film lose part of their bonds with their neighbours, which breaks the original symmetry of the crystal. We have studied in detail how different types of surfaces (for example, aluminium-silicon or gadolinium-aluminium layers) affect the magnetic properties. It turned out that even under such conditions the antiferromagnetic order with spin alternation between neighbouring layers remains the most energetically favourable. This gives hope that ultrathin GdAlSi films can be integrated into nanodevices without loss of key properties.
We confirmed the preservation of the signs of altermagnetism at the nanoscale by modelling films of different thicknesses - from four layers to half a monolayer - and showed how the gradual disappearance of "bulk" properties affects the electronic states. For example, in the thinnest films, the clear separation between atoms in the centre and on the surface disappears: they are all equally affected by the broken symmetry. Another result obtained is a sharp increase in the concentration of charge carriers in GdAlSi monolayers compared to the bulk material. This means that thin films can conduct current more efficiently, which is critical for miniaturised electronic components.
Thus, the properties we have discovered in thin films, which exhibit unique altermagnetic behaviour, open the way to the creation of memory elements, sensors or logic circuits, where the spin properties of the material determine the fast and efficient operation of devices without heating losses and in a non-volatile mode.
The focus of the new research is on ultrathin GdAlSi (gadolinium-aluminum-silicon) metal films, which approach the thickness of several layers. Using computer simulations, we have studied how the material's altermagnetic properties evolve in the transition from bulk crystals to nanometer layers. It turned out that the key feature of altermagnetism - the direction-dependent spin-dependent splitting of electronic states - is preserved even in films a couple of nanometers thick. This splitting arises from the special symmetry of the crystal, where the magnetic moments on gadolinium atoms alternate in strict order between layers while preserving rotational symmetry and translation. For example, at certain points of the Brillouin zone, the electron spins abruptly change direction - as if the compass arrow suddenly flips.
However, when the film thickness is reduced to one unit cell, the effects characteristic of the bulk material begin to weaken. The reason is the influence of the surface: atoms at the edges of the film lose part of their bonds with their neighbours, which breaks the original symmetry of the crystal. We have studied in detail how different types of surfaces (for example, aluminium-silicon or gadolinium-aluminium layers) affect the magnetic properties. It turned out that even under such conditions the antiferromagnetic order with spin alternation between neighbouring layers remains the most energetically favourable. This gives hope that ultrathin GdAlSi films can be integrated into nanodevices without loss of key properties.
We confirmed the preservation of the signs of altermagnetism at the nanoscale by modelling films of different thicknesses - from four layers to half a monolayer - and showed how the gradual disappearance of "bulk" properties affects the electronic states. For example, in the thinnest films, the clear separation between atoms in the centre and on the surface disappears: they are all equally affected by the broken symmetry. Another result obtained is a sharp increase in the concentration of charge carriers in GdAlSi monolayers compared to the bulk material. This means that thin films can conduct current more efficiently, which is critical for miniaturised electronic components.
Thus, the properties we have discovered in thin films, which exhibit unique altermagnetic behaviour, open the way to the creation of memory elements, sensors or logic circuits, where the spin properties of the material determine the fast and efficient operation of devices without heating losses and in a non-volatile mode.