Wafer-thin magnetic materials developed

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A wafer-thin ferrimagnet – in which molecules with different magnetic centres arrange themselves on a gold surface to form a checkerboard pattern – has been produced for the first time, claim researchers from the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute (PSI).

According to the team, 2D ferrimagnets could be a promising material for new types of data storage, sensors or for use in a quantum computer, since the magnetic properties of the molecular building blocks can be individually investigated and modified.

Ferrimagnets are composed of two centres which are magnetised at different strengths and point in opposing directions. It has, however, so far not been possible to produce 2D ferrimagnets.

To solve this problem, the researchers produced ‘phthalocyanines’ – hydrocarbon compounds with different magnetic centres composed of iron and manganese. When these phthalocyanines are applied to a gold surface, they arrange themselves into a checkerboard pattern in which molecules with iron and manganese centres alternate.

The researchers have proven that the surface is magnetic, and that the magnetism of the iron and manganese is of different strengths and appears in opposing directions – all characteristics of a ferrimagnet.

"The decisive factor of this discovery is the electrically conductive gold substrate, which mediates the magnetic order," explained Dr Jan Girovsky from the PSI. "Without the gold substrate, the magnetic atoms would not sense each other and the material would not be magnetic."

The experiments were conducted at various temperatures and therefore provide evidence of the strength of the magnetic coupling in the new magnetic material. Model calculations indicated that special electrons attached to the surface in the gold substrate are responsible for this type of magnetism.