Abstract
Quaternary oxychlorides derived from Ruddlesden-Popper 3d transition metal oxides offer a route to cleavable crystals with bulk antiferromagnetic ordering temperatures reaching at least 550 K. Here, we study the magnetic, optical, and mechanical behavior of Sr2FeO3Cl, Ca2FeO3Cl, Ca3Fe2O5Cl2, and Sr3Fe2O5Cl2. Through optical absorption measurements, we show that these antiferromagnetic semiconductors have optical band gaps of ≈2.1(1)eV. The magnetic ordering symmetries and temperatures were probed by neutron powder diffraction and Mössbauer spectroscopy on polycrystalline samples, demonstrating Néel temperatures (TN) near room temperature in the single layer Sr2FeO3Cl (TN≈311K) and Ca2FeO3Cl (TN≈360K), and the double-layer compound Sr3Fe2O5Cl2 has TN≈545K. The high-spin moments of Fe3+ lie within the basal plane and the magnetic structures are compensated within each magnetic layer and characterized by magnetic propagation vectors k=(12120). Magnetization results demonstrate the quasi-2D nature of the magnetism, with a broad maximum in the susceptibility near 2TN for Sr2FeO3Cl. Scotch tape tests and mechanical exfoliation onto SiO2 confirm the micaceous nature of these crystals with cleavage down to a single unit cell (two magnetic layers) achieved for Sr3Fe2O5Cl2. This paper highlights strong antiferromagnetic interactions, semiconducting band gaps, and cleavability of quaternary Fe-based oxychlorides and motivates future work on crystals and exfoliated flakes of these and related oxyhalide systems.
| Original language | English |
|---|---|
| Article number | 034002 |
| Journal | Physical Review Materials |
| Volume | 9 |
| Issue number | 3 |
| DOIs | |
| State | Published - Mar 2025 |
Funding
This work was supported by the U. S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. This research used resources at the High Flux Isotope Reactor, a U.S. DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. The beam time was allocated to HB-2A (POWDER) on Proposal No. IPTS-29118. Exfoliation efforts (D.O., X.X.) were supported by Air Force Office of Scientific Research (AFOSR) Multidisciplinary University Research Initiative (MURI) program, Grant No. FA9550- 19-1-0390. Atomic force microscopy analysis (DO) was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, EPSCoR, and Materials Sciences and Engineering Division under Award No. DE-SC0025319. Optical measurements (B.M.L. and S.J.M.) were supported by the National Science Foundation, under Grant No. CMMI-2001888. This work was supported by the U. S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. This research used resources at the High Flux Isotope Reactor, a U.S. DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. The beam time was allocated to HB-2A (POWDER) on Proposal No. IPTS-29118. Exfoliation efforts (D.O., X.X.) were supported by Air Force Office of Scientific Research (AFOSR) Multidisciplinary University Research Initiative (MURI) program, Grant No. FA9550- 19-1-0390. Atomic force microscopy analysis (DO) was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, EPSCoR, and Materials Sciences and Engineering Division under Award No. DE-SC0025319. Optical measurements (B.M.L. and S.J.M.) were supported by the National Science Foundation, under Grant No. CMMI-2001888. We are grateful to R. Synowicki for assistance with ellipsometry measurements from the and films. We thank M. Gibertini for useful discussions regarding the Materials Cloud 2D crystals database. Finally, we thank A. Christianson and J. Yan for useful discussions.