A Triangular Frustrated Eu(II)–Organic Framework for Sub-Kelvin Magnetic Refrigeration
Attaining sub-Kelvin temperatures remains technologically challenging and often relies on the scarce resource <sup>3</sup>He, unless employing adiabatic demagnetization refrigeration. Herein, the active coolant typically consists of weakly coupled paramagnetic ions, whose magnetic interaction strengths are comparable in energy to the relevant temperature regime of cooling. Such interactions depend strongly on inter-ion distances, fundamentally hindering the realization of dense coolants for sub-Kelvin refrigeration. We present a magnetically concentrated triangular coordination network, Eu<sub>0.9</sub>Ba<sub>0.1</sub>I<sub>2</sub>(pyrazine)<sub>3</sub>, featuring the large <i>s</i> = 7/2 moment of Eu(II). Electron paramagnetic resonance, magnetization, and heat capacity measurements reflect antiferromagnetic correlations between the Eu(II) ions and a dominant easy-plane magnetic anisotropy. The ensuing geometric frustration prevents entropy-annihilating magnetic order down to at least 0.17 K. This remarkably low operational temperature for a low-dimensional, molecule-based magnetic refrigerant opens possibilities for on-chip cryogenic refrigeration, especially in scenarios where established inorganic refrigerants cannot be utilized.
Authors
- Maja A. Dunstan (ORCID: https://orcid.org/0000-0001-9742-3170)
- Anna Schannong Manvell (ORCID: https://orcid.org/0000-0003-0406-5437)
- Høgni Weihe (ORCID: https://orcid.org/0000-0001-6194-1486)
- Jakub Hrubý (ORCID: https://orcid.org/0000-0003-4947-3688)
- Marco Evangelisti (ORCID: https://orcid.org/0000-0002-8028-9064)
- David Gracia (ORCID: https://orcid.org/0000-0002-3511-3510)
- E. Palacios (ORCID: https://orcid.org/0000-0003-3567-7030)
- Stephen Hill (ORCID: https://orcid.org/0000-0001-6742-3620)
- Mariusz Kubus (ORCID: https://orcid.org/0000-0002-1764-0376)
- Kasper S. Pedersen (ORCID: https://orcid.org/0000-0002-4381-4544)
- James N. McPherson (ORCID: https://orcid.org/0000-0003-0628-7631)
- Jürgen Schnack (ORCID: https://orcid.org/0000-0003-0702-2723)
Institutions
- Florida State University (US)
- University of Copenhagen (DK)
- Bielefeld University (DE)
- Universidad de Zaragoza (ES)
- Instituto de Nanociencia y Materiales de Aragón (ES)
- National High Magnetic Field Laboratory (US)
- Institut für Technische und Angewandte Physik (Germany) (DE)
- Technical University of Denmark (DK)
Publication Details
- Journal
- Journal of the American Chemical Society
- Published
- 2025-01-22
- DOI
- https://doi.org/10.1021/jacs.4c17003
- Citations
- 8
- Primary Topic
- Magnetic and transport properties of perovskites and related materials
- Type
- article
- Field-Weighted Citation Impact
- 3.42
Funders
- Natur og Univers, Det Frie Forskningsråd
- Villum Fonden
- Center for Dark Energy Biosphere Investigations
- Carlsbergfondet
- Ministerio de Ciencia, Tecnología e Innovación Productiva
- Gobierno de Aragón
- European Regional Development Fund