Materials that combine magnetic order with other desirable physical attributes could find transformative applications in spintronics, quantum sensing, low-density magnets and gas separations. Among potential multifunctional magnetic materials, metal–organic frameworks, in particular, bear structures that offer intrinsic porosity, vast chemical and structural programmability, and the tunability of electronic properties. Nevertheless, magnetic order within metal–organic frameworks has generally been limited to low temperatures, owing largely to challenges in creating a strong magnetic exchange. Here we employ the phenomenon of itinerant ferromagnetism to realize magnetic ordering at TC = 225 K in a mixed-valence chromium(ii/iii) triazolate compound, which represents the highest ferromagnetic ordering temperature yet observed in a metal–organic framework. The itinerant ferromagnetism proceeds through a double-exchange mechanism, which results in a barrierless charge transport below the Curie temperature and a large negative magnetoresistance of 23% at 5 K. These observations suggest applications for double-exchange-based coordination solids in the emergent fields of magnetoelectrics and spintronics.
Subscribe to Journal
Get full journal access for 1 year
only $4.92 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Tax calculation will be finalised during checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
Gutfleicsch, O. et al. Magnetic materials and devices for the 21st century: stronger, lighter and more energy efficient. Adv. Mater. 23, 821–842 (2011).
Felser, C., Fecher, G. H. & Balke, B. Spintronics: a challenge for materials science and solid-state chemistry. Angew. Chem. Int. Ed. 46, 668–699 (2007).
Coronado, E., Palacio, F. & Veciana, J. Molecule-based magnetic materials. Angew. Chem. Int. Ed. 42, 2570–2572 (2003).
Kübler, J. Theory of Itinerant Electron Magnetism (Oxford Univ. Press, 2000).
Zener, C. Interaction between the d-shells in the transition metals. II. Ferromagnetic compounds of manganese with perovskite structure. Phys. Rev. 82, 403–405 (1951).
Briceño, G., Chang, H., Sun, X., Schultz, P. G. & Xiang, X.-D. A class of cobalt oxide magnetoresistance materials discovered with combinatorial synthesis. Science 270, 273–275 (1995).
Şaşıoğlu, E., Sandratskii, L. M. & Bruno, P. Role of conduction electrons in mediating exchange interactions in Mn-based Heusler alloys. Phys. Rev. B 77, 064417 (2008).
Yaghi, O. M. et al. Reticular synthesis and the design of new materials. Nature 423, 705–714 (2003).
Calbo, J., Golomb, M. J. & Walsh, A. Redox-active metalo-organic frameworks for energy conversion and storage. J. Mater. Chem. A 7, 16571–16597 (2019).
Yin, Z., Wan, S., Yang, J., Kurmoo, M. & Zeng, M.-H. Recent advances in post-synthetic modification of metal–organic frameworks: new types and tandem reactions. Coord. Chem. Rev. 378, 500–512 (2019).
Dechambenoit, P. & Long, J. R. Microporous magnets. Chem. Soc. Rev. 40, 3249–3265 (2011).
Thorarinsdottir, A. E. & Harris, T. D. Metal–organic framework magnets. Chem. Rev. 120, 8716–8789 (2020).
Kosaka, W. et al. Gas-responsive porous magnet distinguishes the electron spin of molecular oxygen. Nat. Commun. 9, 5420 (2018).
Ruiz, E., Rodríguez-Fortea, A., Alvarez, S. & Verdaguer, M. Is it possible to get high TC magnets with Prussian blue analogues? A theoretical prospect. Chem. Eur. J. 11, 2135–2144 (2005).
Mallah, T., Thiébaut, S., Verdaguer, M. & Veillet, P. High-TC molecular-based magnets: ferrimagnetic mixed-valence chromium(iii)–chromium(ii) cyanide with TC at 240 and 190 Kelvin. Science 262, 1554–1557 (1993).
Ferlay, S., Mallah, T., Ouahès, R., Veillet, P. & Verdaguer, M. A room-temperature organometallic magnet based on Prussian blue. Nature 378, 701–703 (1995).
Holmes, S. M. & Girolami, G. S. Sol–gel synthesis of KVii[Criii(CN)6]·2H2O: a crystalline molecule-based magnet with a magnetic ordering above 100 °C. J. Am. Chem. Soc. 121, 5593–5594 (1999).
Manriquez, J. M., Yee, G. T., McLean, R. S., Epstein, A. J. & Miller, J. S. A room-temperature molecular/organic-based magnet. Science 252, 1415–1417 (1991).
Bechlar, B. et al. High-spin ground states via electron delocalization in mixed-valence imidazolate-bridged divanadium complexes. Nat. Chem. 2, 362–368 (2010).
Gaudette, A. I. et al. Electron hopping through double-exchange coupling in a mixed-valence diiminobenzoquinone-bridged Fe2 complex. J. Am. Chem. Soc. 137, 12617–12626 (2015).
Schulze, B. & Schubert, U. S. Beyond click chemistry—supramolecular interactions of 1,2,3-triazoles. Chem. Soc. Rev. 43, 2522–2571 (2014).
Aubrey, M. L. et al. Electron delocalization and charge mobility as a function of reduction in a metal–organic framework. Nat. Mater. 17, 625–632 (2018).
Zhang, J. P., Zhang, Y. B., Lin, J. B. & Chen, X. M. Metal azolate frameworks: from crystal engineering to functional materials. Chem. Rev. 112, 1001–1033 (2012).
Park, J. G. et al. Charge delocalization and bulk electronic conductivity in the mixed-valence metal–organic framework Fe(1,2,3-triazolate)2(BF4)x. J. Am. Chem. Soc. 140, 8526–8534 (2018).
Brunschwig, B. S., Creutz, C. & Sutin, N. Optical transitions of symmetrical mixed-valence systems in the class II–III transition regime. Chem. Soc. Rev. 31, 168–184 (2002).
Gándara, F. et al. Porous, conductive metal–triazolates and their structural elucidation by the charge-flipping method. Chem. Eur. J. 18, 10595–10601 (2012).
Zhou, X.-H., Peng, Y.-H., Du, X.-D., Zuo, J.-L. & You, X.-Z. Hydrothermal syntheses and structures of three novel coordination polymers assembled from 1,2,3-triazolate ligands. Cryst. Eng. Comm. 11, 1964–1970 (2009).
Collman, J. P. et al. Synthetic, electrochemical, optical, and conductivity studies of coordination polymers of iron, ruthenium, and osmium octaethylporphyrin. J. Am. Chem. Soc. 109, 4606–4614 (1987).
Tanner, D. B., Jacobsen, C. S., Garito, A. F. & Heeger, A. J. Infrared studies of the energy gap in tetrathiofulvalene-tetracyanoquinodimethane (TTF-TCNQ). Phys. Rev. B 13, 3381–3404 (1976).
Motokawa, N., Miyasaka, H., Yamashita, M. & Dunbar, K. R. An electron-transfer ferromagnet with TC = 107 K based on a three-dimensional [Ru2]2/TCNQ system. Angew. Chem. Int. Ed. 47, 7760–7763 (2008).
Stone, K. H. et al. Mnii(TCNE)3/2(I3)1/2—a 3D network-structured organic-based magnet and comparison to a 2D analog. Adv. Mater. 22, 2514–2519 (2010).
Kessler, J. Polarized Electrons (Springer, 1985).
Efros, A. L. & Shklovskii, B. I. Coulomb gap and low temperature conductivity of disordered systems. J. Phys. C 8, L49–L56 (1975).
Raju, N. P. et al. Anomalous magnetoresistance in high-temperature organic-based magnetic semiconducting V(TCNE)x films. J. Appl. Phys. 93, 6799 (2003).
Coronado, E., Prieto-Ruiz, J. P. & Prima-Garcia, H. Spin polarization in electrodeposited thin films of the molecule-based magnetic semiconductor Cr5.5(CN)12·11.5H2O. Chem. Commun. 49, 10145–10147 (2013).
Lu, Y. et al. Thin-film deposition of an organic magnet based on vanadium methyl tricyanoethylenecarboxylate. Adv. Mater. 26, 7632–7636 (2014).
Black, N. et al. Giant negative magnetoresistance in Ni(quinoline-8-selenoate)2. Phys. Chem. Chem. Phys. 20, 514–519 (2018).
Coey, J. M. D. & Venkatesan, M. Half-metallic ferromagnetism: example of CrO2. J. Appl. Phys. 91, 8345–8350 (2002).
Xiao, J. Q., Jian, J. S. & Chien, C. L. Giant magnetoresistance in nonmultilayer magnetic systems. Phys. Rev. Lett. 68, 3749–3752 (1992).
Coelho, A. A. TOPAS-Academic v. 5 (Coelho Software, 2017).
Huq, A. et al. POWGEN: rebuild of a third-generation powder diffractometer at the Spallation Neutron Source. J. Appl. Cryst. 52, 1199–1201 (2019).
This research was supported by the National Science Foundation (NSF) Award no. DMR-1611525, with the exception of the measurement and analysis of the magnetic data, which were supported by the Nanoporous Materials Genome Center of the US Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences under Award no. DE-FG02-17ER16362. Powder X-ray diffraction data were collected at Beamline 11-BM at the APS, operated by Argonne National Laboratory, and beamline BM31 at the ESRF. We are grateful to our local contact at the ESRF for providing assistance in using beamline BM31. Use of the APS at Argonne National Laboratory was supported by US Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract no. DE-AC02-06CH11357. Data from Beamline 11-BM were collected as part of the 2018 Modern Methods in Rietveld Refinement and Structural Analysis workshop, a school supported by the US National Committee for Crystallography and the American Crystallographic Association. Neutron diffraction data were collected at the POWGEN beamline at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. Soft X-ray absorption spectroscopy data were collected at Beamline 8.0.1 at the Advanced Light Source of Lawrence Berkeley National Laboratory, a Department of Energy Office of Science User Facility under Contract no. DE-AC02-05CH11231. Electronic structure calculations utilized an award of computer time provided by the ASCR Leadership Computing Challenge (ALCC) program and resources of the National Energy Research Scientific Computing Center, a US Department of Energy Office of Science User Facility operated under Contract no. DE-AC02-05CH11231. Additional computation resources were provided by the Minnesota Supercomputing Institute at the University of Minnesota. T.R. thanks the Welch Foundation (Grant no. N-2012-20190330) for funding. In addition, we thank J. Oktawiec, S. H. Lapidus, X. Wenqian, P. Khalifah, Q. Zhang, M. J. Kirkham, Y.-S. Liu and G. Ren for discussions and experimental assistance, and T.D.H. for editorial assistance. We also thank the National Science Foundation and National GEM Consortium for providing graduate fellowship supports for J.G.P. and B.A.C., respectively.
The authors declare no competing interests.
Peer review information Nature Chemistry thanks Talal Mallah and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
a,b Scanning electron microscopy images of microcrystalline Cr(tri)2(CF3SO3)0.33 powder. Octahedron-shaped crystals have an average edge dimension of ~0.5 μm. Scale bars 2 μm (a) and 1 μm (b).
a, N2 adsorption isotherm collected at 77 K for Cr(tri)2(CF3SO3)0.33. Closed and open data points represent adsorption and desorption, respectively. b, Infrared data collected at 150 K (blue) and 300 K (red) and the difference plot (green) for Cr(tri)2(CF3SO3)0.33. Source data
a, Variable-temperature magnetic susceptibility data (χM) for Cr(tri)2(CF3SO3)0.33 collected under the applied dc field of 25 Oe. Data plotted as 1/χM versus temperature. Curie-Weiss fit to the data between 300 K and 350 K is shown by a black solid line, with fitting parameters described in the main text. b-f, Variable-temperature in-phase (χ”) and out-of-phase (χ”) ac magnetic susceptibility of Cr(tri)2(CF3SO3)0.33 at selected frequencies of 4 Oe ac oscillating magnetic field and zero dc magnetic field. Source data
a, Magnetic moments (µB mol−1) for the ferromagnetic state. b, Atomic charge for the ferromagnetic state in atomic units. c, Magnetic moments (µB mol−1) for the antiferromagnetic state. d, Atomic charge for the antiferromagnetic state in atomic units. Atomic properties shown as a gradient from blue to white to red. Negative magnetic moments indicate spin-down contributions.
a-d, Variable-temperature log(σ) data of Cr(tri)2(CF3SO3)0.33 plotted versus 1/T0.25 (a), 1/T0.5 (b), and 1/T and fitted with three-dimensional variable-range hopping, Efros-Shklovskii variable-range hopping, and Arrhenius models, respectively (c, d). For clarity, log(σ) versus 1/T plot (c) has been zoomed-in to the intermediate temperature region (d) where conductivity exhibits a weak temperature dependence. Source data
Definition of compound, additional methods, additional discussion, references, Supplementary Tables 1 and 2 and Figs. 1–7.
Supplementary PXRD Data containing synchrotron powder X-ray diffraction data (.xye) and input (.inp) files used for performing Rietveld refinements in Supplementary Figure 1.
Supplementary computational data, source data for Supplementary Figure 4.
Statistical source data for Figure 2a,b.
Statistical source data for Figure 3a,b,c.
Statistical source data for Figure 4e,f.
Statistical source data for Extended Data Figure 2.
Statistical source data for Extended Data Figure 3.
Statistical source data for Extended Data Figure 5.
About this article
Cite this article
Park, J.G., Collins, B.A., Darago, L.E. et al. Magnetic ordering through itinerant ferromagnetism in a metal–organic framework. Nat. Chem. (2021). https://doi.org/10.1038/s41557-021-00666-6