arXiv subjects

Danil A. Myakotnikov

Publications and source records attributed to Danil A. Myakotnikov.

2 recordsLinked to original sources

arXiv2025

Anomalous lattice specific heat and rattling phonon modes in quadruple perovskites

Experimental data on the specific heat $C_p$ of quadruple perovskites ACu$_3$Fe$_2$Re$_2$O$_{12}$ (A = Mn, Cu, La, Ce, Dy) are presented, demonstrating an anomalous concave-down $C_p/T$ vs. $T^2$ curve and a bell-shaped feature in $β(T) = (C_p - γT)/T^3$ plotted against $T$ on a logarithmic scale. This feature is most pronounced for A = Cu and Mn. These findings can be explained by the rattling phenomenon, previously identified in other systems such as filled skutterudites and $β$-pyrochlores. Using first-principles DFT+U calculations, the presence of a rattling mode in A = Mn system is directly confirmed. A qualitative interpretation of the rattling mechanism in terms of a pseudo-Jahn-Teller effect is proposed.

cond-mat.mtrl-sci↗

arXiv2024

Importance of the indirect exchange interaction $via$ $s$-states in altermagnetic HgMnO$_3$

The electronic and magnetic properties of recently synthesized new perovskite phase of HgMnO$_3$ are studied. By means of $ab$ $initio$ DFT calculations this material was shown to be altermagnetic. We discuss features of its electronic structure and unveil the physical mechanism of anomalous suppression of antiferromagnetic exchange interaction in this material. While it is tempting to ascribe unexpectedly weak exchange interaction between nearest neighbors to crystal structure distortions, this is the indirect ferromagnetic exchange via Hg $6s$ states, which strongly affects the magnetic properties. This effect can be important not only for HgMnO$_3$, but also for many other transition metal compounds having empty $s$ states, placed not far above the Fermi level.

cond-mat.str-el↗