By Josh Perry, Editor
[email protected]

Scientists from the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN) in Krakow, the Karlsruhe (Germany) Institute of Technology (KIT), the Paul Drude Institut für Festkörperelektronik in Berlin and the DESY research Centre in Hamburg calculated the interactions between electrons at the interface of ferromagnetic metals and semiconductors, which determine heat flow.

Microscopic image of the GaAs/Fe3Si interface (GaAs marked in green, Fe3Si in yellow; the protective germanium layer in brown). (IFJ PAN)

According to a report from the IFJ PAN, this new study fills a thermal gap in the knowledge base of these materials and paves the way for future development of spintronics (devices powered by the spin currents).

Researchers used the PHONON computer system, created two decades ago at the IFJ PAN, to calculate the force of atomic vibrations at the interface of the two materials in the crystal lattice.

“The dynamics of atoms in crystals is not random,” the article explained. “Crystalline materials are characterized by a long-range order. As a consequence, the motion of atoms is not chaotic here, but it follows certain, sometimes very complex, patterns. Transverse acoustic waves are mainly responsible for heat transfer. This means that when analyzing the lattice dynamics, the researchers had to pay special attention to the atomic vibrations occurring in the plane parallel to the interface. If the vibration waves of the atoms in both materials were matched to each other, heat would effectively flow through the interface.”

The research was recently published in Physical Review B. The abstract stated:

“We report a systematic lattice dynamics study of the technologically important Fe3Si/GaAs heterostructure for Fe3Si layer thicknesses of 3, 6, 8, and 36 monolayers. The Fe-partial phonon density of states obtained by nuclear inelastic scattering exhibits up to a twofold enhancement of the low-energy phonon states compared to the bulk material for layer thicknesses of 8 monolayers and below.

“First-principles calculations explain the observed effect by interface-specific phonon states originating from the significantly reduced atomic force constants and allow for achieving a comprehensive understanding of the lattice dynamics of epitaxial strain-free interfaces.”