Speaker
Description
In the Eu–Pd–Sn system some novel compounds have been discovered, showing a stable Eu$^{2+}$ magnetic state and complex magnetic structures, e.g. EuPdSn$_2$, Eu$_2$Pd$_2$Sn and EuPd$_2$Sn$_4$ [1–5]. The scenarios of complex and anisotropic magnetism are not expected for Eu$^{2+}$ because of its spin $S=7/2$ and orbital $L = 0$ numbers precluding the presence of crystal electric field effects. Following these studies, in this work we report on the first results of crystal structure and physical properties of the novel Eu$_2$Pd$_3$Sn$_5$ compound.
Eu$_2$Pd$_3$Sn$_5$ crystallizes in the orthorhombic $Ibam$ space group with lattice parameters $a = 11.079(3)$, $b = 12.900(4)$, $c = 6.4958(17)$ Å, being a new representative of the U$_2$Co$_3$Si$_5$ prototype. Atoms are distributed among 6 atomic sites, one ($8j$) occupied by Eu, two ($4b$, $8j$) by Pd and three ($4a$, $8g$, $8j$) by Sn species; the rare-earth Eu atoms are distributed as zigzag chains along both sides of the ($bc$) plane.
The temperature dependence of the $\chi$(T) magnetic susceptibility of Eu$_2$Pd$_3$Sn$_5$ measured in magnetic field $1$ T revealed a Curie-Weiss behavior down to $20$ K. The effective magnetic moment for Eu$_2$Pd$_3$Sn$_5$ is $\mu_{eff} = 7.85$ $\mu_B$ in good agreement with that of the free ion Eu$^{2+}$ value ($\mu_{eff} = 7.94$ $\mu_B$). The paramagnetic Curie temperature obtained from the fit is $\Theta_p = 8.72$ K, indicating the presence of ferromagnetic interaction in the sample. In $\chi(T)$ dependencies for low magnetic field $B = 0.01$ T two anomalies are present – antiferromagnetic-like at $13.8$ K and ferromagnetic-like at about $5$ K. The first one is completely absent with applying the magnetic field of $1$ T. Moreover, the $\chi(T)$ behavior for applied magnetic fields $B\geq 1$ T is typical of a ferromagnetic material. This scenario is supported with $C_p(T)$ specific heat measurements, where two anomalies ($\sim 13$ K and $5$ K) are present only for lower field $B \leq 1$ T. The $\lambda$-like anomaly at $\sim 13$ K is shifted in temperature with applying magnetic field and additionally the maximum becomes significantly broader. This behavior is usually found in ferromagnetic materials. Our results indicate a complex interplay between antiferromagnetism and ferromagnetism in novel Eu$_2$Pd$_3$Sn$_5$ compound.
Acknowledgements
This work was supported by the project VEGA 1/0511/24. Financial support from the Ministry of Higher Education and Scientific Research of Tunisia is also gratefully acknowledged
References
[1] I. Čurlík et al., “Crystal structure and physical properties of the two stannides EuPdSn2 and YbPdSn2,” Journal of Physics: Condensed Matter, vol. 30, no. 49. IOP Publishing, p. 495802, Nov. 15, 2018. https://doi.org/10.1088/1361-648x/aae7ae
[2] I. Čurlík et al., “The Magnetic Field Induced Ferromagnetism in EuPd2Sn4 Novel Compound,” physica status solidi (b), vol. 258, no. 6. Wiley, Apr. 15, 2021. https://doi.org/10.1002/pssb.202000633
[3] J.G. Sereni et al.,"Evidence for magnetic dimers and skyrmion lattice formation in Eu2Pd2Sn," Physical Review B, vol. 108, no. 1. American Physical Society (APS), Jul. 24, 2023. https://doi.org/10.1103/physrevb.108.014427
[4] A. Martinelli et al.,"Incommensurate magnetic cycloidal order in noncentrosymmetric Eu2Pd2Sn," Physical Review B, vol. 109, no. 10. American Physical Society (APS), Mar. 21, 2024. https://doi.org/10.1103/physrevb.109.104424
[5] A. Martinelli et al., “Magnetic phase separation in the EuPdSn2ground state,” Journal of Materials Chemistry C, vol. 11, no. 23. Royal Society of Chemistry (RSC), pp. 7641–7653, 2023. https://doi.org/10.1039/d3tc00764b
