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Instruments / Technical Area	Publication Details	Published
B18-Core EXAFS	Novel Ir1–xCoxO2 thin films: growth and characterization M. A. Laguna-Marco , Julia Herrero-Albillos , M. H. Aguirre , M. Rueda-Jiménez , I. Mikulska Journal Of Alloys And Compounds 4 DOI: 10.1016/j.jallcom.2023.171975 Diamond Proposal Number(s): [32410] Open Access Show Abstract ▼ Abstract: Ir1–xCoxO2 thin films have been prepared by reactive co–sputtering deposition at room temperature. Composition, structure, electronic properties and electric and magnetic behavior have been analyzed by different techniques including XRR, XRD, TEM microscopy, SQUID magnetometry, electrical resistivity and XAS spectroscopy. After annealing, an Ir1–xCoxO2 substitutional solid solution phase with rutile crystal structure was achieved for a wide Co-doping range 0 ≤ x ≤ 0.6. Starkly departing from the highly insulating behavior of CoO and Co3O4, the electrical resistivity at room temperature of our films is only slightly higher than that of IrO2. Likewise, our work shows that the magnetic response of the doped films is very similar to that of the paramagnetic parent IrO2. Neither ferromagnetism nor enhanced paramagnetism is observed. XAS spectra indicate a Co3+ oxidation state and, correspondingly, an oxidation state of ∼5+ for Ir ions in the polycrystalline Ir0.6Co0.4O2 film. By application of sum rules, a 13% increase in the spin–orbit coupling is found despite the lattice shrinkage causes a detrimental bandwidth broadening.	Sep 2023
I20-Scanning-X-ray spectroscopy (XAS/XES)	Dimensionality-driven metal–insulator transition in spin–orbit-coupled IrO2 E. Arias-Egido , M. A. Laguna-Marco , C. Piquer , P. Jimenez-Cavero , I. Lucas , L. Morellon , F. Gallego , A. Rivera-Calzada , M. Cabero , J. Santamaría , G. Fabbris , D. Haskel , R. Boada , S. Diaz-Moreno Nanoscale DOI: 10.1039/D1NR04207F Diamond Proposal Number(s): [17266] Open Access Show Abstract ▼ Abstract: A metal–insulator transition is observed in spin–orbit-coupled IrO2 thin films upon reduction of the film thickness. In the epitaxially grown samples, the critical thickness (t ∼ 1.5–2.2 nm) is found to depend on growth orientation (001), (100) or (110). Interestingly from the applied point of view, the insulating behavior is found even in polycrystalline ultrathin films. By analyzing the experimental electrical response with various theoretical models, we find good fits to the Efros–Shklovskii-VRH and the Arrhenius-type behaviors, which suggests an important role of electron correlations in determining the electrical properties of IrO2. Our magnetic measurements also point to a significant role of magnetic order. Altogether, our results would point to a mixed Slater- and Mott-type of insulator.	Oct 2021
I20-Scanning-X-ray spectroscopy (XAS/XES)	Toward the optimized spintronic response of Sn-doped IrO2 thin films Eduardo Arias-Egido , María Angeles Laguna-Marco , Cristina Piquer , Roberto Boada , Sofia Diaz-Moreno Advanced Functional Materials 7 DOI: 10.1002/adfm.201806754 Diamond Proposal Number(s): [15016] Show Abstract ▼ Abstract: Amorphous and polycrystalline Sn‐doped IrO2 thin films, Ir1‐xSnxO2, are grown for the first time. Their electrical response and strength of the spin–orbit coupling are studied in order to better understand and tailor its performance as spin current detector material. These experiments prove that the resistivity of IrO2 can be tuned over several orders of magnitude by controlling the doping content in both the amorphous and the polycrystalline state. In addition, growing amorphous samples increase the resistivity, thus improving the spin current to charge current conversion. As far as the spin–orbit coupling is concerned, the system not only remains in a strong spin–orbit coupling regime but it seems to undergo a slight enhancement in the amorphous state as well as in the Sn‐doped samples.	Jan 2019
	Magnetic clusters on the verge of long range ferromagnetism in Lu(Fe0.75Al0.25)2 and Lu(Fe0.50Al0.50)2 alloys C. Piquer , L. Fernández Barquín , J. Chaboy , D. Alba-Venero , M. A. Laguna-Marco , R. Boada , J. Sánchez-Marcos , I. Puente-Orench Journal Of Alloys And Compounds 695, 704 - 714 DOI: 10.1016/j.jallcom.2016.10.181 Show Abstract ▼ Abstract: Lu(Fe0.75Al0.25)2 and Lu(Fe0.50Al0.50)2 alloys have been produced by arc-melting. DC and AC magnetization, Mössbauer spectroscopy, specific heat and neutron diffraction experiments have been performed to determine their magnetic ground state. DC magnetization curves measured at low fields (H < 1 kOe) evidence two peaks, at TSRO and Tf, and magnetic irreversibility. The peak at TSRO vanishes and the one at Tf smears out when high fields (H ≥ 1 kOe) are applied. The thermal variation of AC susceptibility shows that both transitions at TSRO and Tf are frequency dependent. Neither magnetic splitting nor broadening is observed in the Mössbauer spectra of both compounds in the Tf < T < TSRO thermal range. A magnetically split spectrum is only observed in Lu(Fe0.75Al0.25)2 for T < Tf. The absence of long range ferromagnetic order in both alloys is confirmed by specific heat and neutron diffraction measurements. The overall interpretation points to a clustered magnetic environment due to the random positions of Fe atoms in the crystallographic cell. At TSRO a short range ferromagnetic order takes place within the clusters, which become frustrated at Tf, when the random anisotropy of the clusters enables their freezing.	Feb 2017

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