High‐Entropy Magnetism of Murunskite

Tolj, Davor; Reddy, Priyanka; Živković, Ivica; Akšamović, Luka; Soh, Jian Rui; Komȩdera, Kamila; Biało, Izabela; Chogondahalli Muniraju, Naveen Kumar; Ivšić, Trpimir; Novak, Mario; Zaharko, Oksana; Ritter, Clemens; LaGrange, Thomas; Tabiś, Wojciech; Batistić, Ivo; Forró, László; Rønnow, Henrik M.; Sunko, Denis K.; Barišić, Neven (2025) High‐Entropy Magnetism of Murunskite. Advanced Functional Materials, 35 (40). ISSN 1616-301X

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Abstract

Murunskite (K2FeCu3S4) bridges the two known families of high-temperature superconductors, cuprates and iron-pnictides, structurally and electronically. Like these families, murunskite exhibits an antiferromagnetic (AF)-like response with an ordered phase below 97 K. The magnetic iron atoms are randomly distributed over one-quarter of the sites in two-dimensional planes, while the remaining sites are occupied by non-magnetic copper, evoking the notion of a high-entropy magnetic alloy. This intriguing magnetic transition is studied by neutron, M & ouml;ssbauer, and X-ray photoelectron spectroscopy (XPS) measurements on single crystals. The AF order has a nearly commensurate quarterzone wave vector. In the paramagnetic state, M & ouml;ssbauer spectroscopy identifies two iron sites, associated with Fe3 + or Fe2 + oxidation states as observed by XPS, which merge into a third site upon cooling, indicating an orbital transition. This cascade of local transitions transforms iron atoms from a fully orbitally and magnetically disordered state to a homogeneously ordered state in inverse space, while still being randomly distributed in real space. This finding challenges the traditional paradigm of magnetism in insulators, which relies on a direct connection between crystal structure and the location of magnetic moments.

Item Type:	Article
Uncontrolled Keywords:	murunskite; orbital transition; high-temperature superconductors
Subjects:	NATURAL SCIENCES > Physics NATURAL SCIENCES > Chemistry NATURAL SCIENCES > Interdisciplinary Natural Sciences
Divisions:	Division of Physical Chemistry
Depositing User:	Ema Buhin Šaler
Date Deposited:	23 Mar 2026 12:28
URI:	http://fulir.irb.hr/id/eprint/11401
DOI:	10.1002/adfm.202500099

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