Publication: Spin transition nanoparticles made electrochemically
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2020-03-07
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Royal Society of Chemistry
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Abstract
Materials displaying novel magnetic ground states signify the most exciting prospects for nanoscopic devices for nanoelectronics and spintronics. Spin transition materials, e.g., spin liquids and spin glasses, are at the forefront of this pursuit; but the few synthesis routes available do not produce them at the nanoscale. Thus, it remains an open question if and how their spin transition nature persists at such small dimensions. Here we demonstrate a new route to synthesize nanoparticles of spin transition materials, gas-diffusion electrocrystallization (GDEx), wherein the reactive precipitation of soluble metal ions with the products of the oxygen reduction reaction (ORR), i.e., in situ produced H_2O_2, OH^-, drives their formation at the electrochemical interface. Using mixtures of Cu^(2+) and Zn^(2+) as the metal precursors, we form spin transition materials of the herbertsmithite family-heralded as the first experimental material known to exhibit the properties of a quantum spin liquid (QSL). Single-crystal nanoparticles of similar to 10-16 nm were produced by GDEx, with variable Cu/Zn stoichiometry at the interlayer sites of Zn_xCu_(4-x)(OH)_6Cl_2. For x = 1 (herbertsmithite) the GDEx nanoparticles demonstrated a quasi-QSL behavior, whereas for x = 0.3 (0.3 < x < 1 for paratacamite) and x = 0 (clinoatacamite) a spin-glass behavior was evidenced. Finally, our discovery not only confirms redox reactions as the driving force to produce spin transition nanoparticles, but also proves a simple way to switch between these magnetic ground states within an electrochemical system, paving the way to further explore its reversibility and overarching implications.
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©2020 Royal Society of Chemistry
G. Pozo acknowledges the funding from the European Union's Horizon 2020 research and innovation programme MSCA-IF-2017, under grant agreement no. 796320 (MAGDEx: Unmet MAGnetic properties in micro and nano-particles by synthesis through gas diffusion electrocrystallisation, (GDEx).; X. Dominguez-Benetton thanks to VITO's strategic research funds and management for the possibility to conduct this pioneering research. GP, RP, JF, and XDB thank the support from the Flemish SIM MaRes programme, under grant agreement no. 150626 (Get-A-Met project). XDB and JF thanks the funding from the European Union's Horizon 2020 research and innovation programme under grant agreement no. 654100 (CHPM2030 project). This work has been supported by the Ministerio Espanol de Economia y Competitividad (MINECO) RTI2018-095856-B-C21, and Comunidad de Madrid S2013/MIT-2850 NANOFRONTMAG projects. We would also like to acknowledge Myriam Mertens for fruitful discussions and her support on XRD analysis, as well as Kristof Tirez and Wilfried Brusten for assistance with analytical measurements.