Electronic inhomogeneity and magnetic polaron formation in Eu-based compounds | Colóquio IFUSP
Data de Início:
quinta-feira, 27 Novembro, 2025 - 16:00
Palestrante:
Prof. Steffen Wirth, Max-Planck-Institute for Chemical Physics of Solids Dresden, Germany
Local:
Auditório Abrahão de Moraes
Sobre o evento:
Materials in which the structural, electronic and magnetic degrees of freedom are entangled can exhibit unexpected or even spectacular physical phenomena like superconductivity or colossal magnetoresistance (CMR). A hallmark of such coupled degrees of freedom is the appearance of distinct electronic phases, along with phase separation and pattern formation. One particular case of electronic inhomogeneity often observed in Eu-containing compounds are magnetic polarons, within which conduction electrons are localized via strong exchange interaction with the Eu 4f moments.
We report on our investigations on three different compounds, all of which exhibit a large CMR effect. The ferromagnetic material EuB6 is presented as a benchmark case for which polaron formation is well established [1]. We then focus on the antiferro-magnetic Zintl compound Eu5In2Sb6 which crystallizes in the non-symmorphic space group Pbam and hence, non-trivial topological properties can be expected. We find a record CMR and strong evidence for the occurrence of polarons in this low-carrier density material [2,3]. The calculated band structures and resultant DOS for the considered antiferromagnetic and ferromagnetic spin structures in Eu5In2Sb6 nicely illustrate how the difference in spin configuration can lead to a reorganization of the small band contributions near the Fermi level EF [4].
Also, EuCd2P2 exhibits an enormous CMR of up to 105 %. We, again, combined locally resolved investigations by Scanning Tunneling Spectroscopy with bulk measurements of the magnetic, thermodynamic and electronic transport properties and find a complex interplay of ferro- and antiferromagnetic interactions at work. The dynamical properties of magnetic polarons are investigated by non-linear transport and SR measurements [5]. The implications of inhomogeneous states in relation to possible scenarios for CMR will be discussed.
*In collaboration with M. V. Ale Crivillero, H. Dawczak-Dębicki, Z. Fisk, S. Krebber, C. Krellner, K. Kliemt, J. Müller, P. F. S. Rosa and U. K. Rößler
References
1. M. Pohlit et al., Phys. Rev. Lett. 120, 257201 (2018).
2. M. V. Ale Crivillero et al., Sci. Rep. 13, 1597 (2023).
3. H. Dawczak-Dębicki et al., Commun. Mater. 5, 248 (2024).
4. M. V. Ale Crivillero et al., Phys. Rev. B 106, 035124 (2022).
5. M. Kopp et al., submitted.
Materials in which the structural, electronic and magnetic degrees of freedom are entangled can exhibit unexpected or even spectacular physical phenomena like superconductivity or colossal magnetoresistance (CMR). A hallmark of such coupled degrees of freedom is the appearance of distinct electronic phases, along with phase separation and pattern formation. One particular case of electronic inhomogeneity often observed in Eu-containing compounds are magnetic polarons, within which conduction electrons are localized via strong exchange interaction with the Eu 4f moments.
We report on our investigations on three different compounds, all of which exhibit a large CMR effect. The ferromagnetic material EuB6 is presented as a benchmark case for which polaron formation is well established [1]. We then focus on the antiferro-magnetic Zintl compound Eu5In2Sb6 which crystallizes in the non-symmorphic space group Pbam and hence, non-trivial topological properties can be expected. We find a record CMR and strong evidence for the occurrence of polarons in this low-carrier density material [2,3]. The calculated band structures and resultant DOS for the considered antiferromagnetic and ferromagnetic spin structures in Eu5In2Sb6 nicely illustrate how the difference in spin configuration can lead to a reorganization of the small band contributions near the Fermi level EF [4].
Also, EuCd2P2 exhibits an enormous CMR of up to 105 %. We, again, combined locally resolved investigations by Scanning Tunneling Spectroscopy with bulk measurements of the magnetic, thermodynamic and electronic transport properties and find a complex interplay of ferro- and antiferromagnetic interactions at work. The dynamical properties of magnetic polarons are investigated by non-linear transport and SR measurements [5]. The implications of inhomogeneous states in relation to possible scenarios for CMR will be discussed.
*In collaboration with M. V. Ale Crivillero, H. Dawczak-Dębicki, Z. Fisk, S. Krebber, C. Krellner, K. Kliemt, J. Müller, P. F. S. Rosa and U. K. Rößler
References
1. M. Pohlit et al., Phys. Rev. Lett. 120, 257201 (2018).
2. M. V. Ale Crivillero et al., Sci. Rep. 13, 1597 (2023).
3. H. Dawczak-Dębicki et al., Commun. Mater. 5, 248 (2024).
4. M. V. Ale Crivillero et al., Phys. Rev. B 106, 035124 (2022).
5. M. Kopp et al., submitted.
Mini autobiografia do palestrante:
Steffen Wirth obtained a doctoral degree (1995) in physics from the Technical University in Dresden. He was a postdoctoral scientist at Trinity College Dublin (1995–1996) and a Feodor Lynen fellow by the Alexander von Humboldt-Foundation, Germany at Florida State University (1996–2000) before becoming a staff member at the Max-Planck- Institute for Chemical Physics of Solids Dresden in 2000. In 2009, he completed his habilitation at TU Dresden and was a visiting professor at the University of Göttingen, Germany. In 2017, he became a Fellow of the American Physical Society (APS). His research focuses on magnetism and superconductivity, with emphasis on strongly correlated electron systems by utilizing scanning tunneling microscopy, magnetic and electronic transport measurements at low temperatures and high magnetic fields.
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