Researchers from the Max Planck Institute for Chemical Physics of Solids in Dresden, Germany, have been investigating a unique metallic compound, Sc$_3$Mn$_3$Al$_7$Si$_5$, which exhibits intriguing magnetic properties. This study, published in the journal Nature Communications, explores the low-temperature spin dynamics of this material, which could have implications for the energy sector, particularly in the development of advanced magnetic materials for energy storage and conversion devices.
The team, led by Dr. R. Guehne and Professor C. Felser, combined various experimental techniques to probe the magnetic behavior of Sc$_3$Mn$_3$Al$_7$Si$_5$. Bulk thermodynamic measurements revealed a significant reduction in magnetic entropy and a negative magnetoresistance, which is a change in electrical resistance in response to an applied magnetic field. This negative magnetoresistance arises from spin scattering, a phenomenon where the spins of electrons interact with each other, affecting the material’s electrical resistance. The researchers also observed that the material’s transport properties are field-dependent, indicating the presence of spin fluctuations, but found no signs of long-range magnetic order.
To gain a more detailed understanding of the local magnetic environment, the researchers employed Nuclear Magnetic Resonance (NMR) measurements. They observed a pronounced enhancement in the nuclear spin-spin relaxation rate ($T_2$) at low temperatures, driven by an indirect internuclear coupling through electronic spin fluctuations. The temperature and distance dependence of these fluctuations suggested the presence of partially gapped low-energy spin excitations. Additionally, the spin-lattice relaxation rate ($T_1^{-1}$) exhibited a Hebel-Slichter-like coherence peak near 10 Kelvin, coinciding with a crossover in resistivity and a subtle heat-capacity anomaly. These observations point to the formation of short-range spin-singlet correlations, a state where pairs of electrons with opposite spins form a correlated state.
The researchers concluded that Sc$_3$Mn$_3$Al$_7$Si$_5$ hosts an unconventional correlated state dominated by frustrated, gapped spin dynamics. This places the material among the rare metallic kagome systems proximate to a quantum spin liquid, a state of matter that has potential applications in quantum computing and advanced magnetic materials for energy technologies. While the direct practical applications for the energy sector are still under investigation, the unique magnetic properties of this material could lead to the development of novel magnetic materials for energy storage and conversion devices, such as advanced batteries and magnetic refrigeration systems.
This article is based on research available at arXiv.