Electronic structure, magnetism and spin fluctuations in the superconducting weak ferromagnet Y4Co3

TL;DR

This study uses first-principles calculations to analyze the electronic structure and magnetism of the superconducting weak ferromagnet Y4Co3, revealing the role of specific cobalt atoms and the influence of spin fluctuations.

Contribution

It provides the first detailed electronic and magnetic analysis of Y4Co3, highlighting the specific cobalt atom responsible for weak ferromagnetism and the importance of spin fluctuations.

Findings

Weak ferromagnetism is mainly due to one cobalt atom on the (2b) site.

Magnetic Co atoms form quasi-one-dimensional chains.

Calculated magnetic moments overestimate experimental values, indicating spin fluctuations.

Abstract

Results of the first principles study on the electronic structure and magnetism of the superconducting weak ferromagnet Y$_4$Co$_3$, are presented. Using the full potential Korringa-Kohn-Rostoker (FP-KKR) method, densities of states, dispersion curves and magnetic moments were calculated for quasi-ordered structural model of the compound in the framework of the local density approximation. Spin-polarized KKR calculations confirm that weak ferromagnetic properties of Y$_4$Co$_3$ can be attributed to only one cobalt atom located on (2b) site in the unit cell, while other twenty Co and Y atoms acts as a diamagnetic environment. Moreover, the magnetic Co atoms form a quasi-one-dimensional chains along $z$ direction. The magnitude of Co(2b) magnetic moment ($0.55~\mu_B$) markedly overestimates the experimental value (0.23~$\mu_B$), which suggests the importance of spin fluctuations in this system. Calculated distribution of spin magnetization in the unit cell provides a background for discussion of the coexistence of ferromagnetism and superconductivity in Y$_4$Co$_3$. Finally, the effect of pressure on magnetism is discussed and compared with experimental data, also supporting weak ferromagnetic behaviors in the system.