SCIENTIFIC HIGHLIGHTS

23 December 2017

José Luis García-Muñoz, Arnau Romaguera, Francois Fauth, Josep Nogués, and Martí Gich*. Chem. Mater., 2017, 29 (22), pp 9705–9713. DOI: 10.1021/acs.chemmater.7b03417

Iron oxides are among the most abundant materials on Earth, and yet there are some of their basic properties which are still not well-established. Here, we present temperature-dependent magnetic, X-ray, and neutron diffraction measurements refuting the current belief that the magnetic ordering temperature of ε-Fe2O3 is ∼500 K, i.e., well below that of other iron oxides such as hematite, magnetite, or maghemite. Upon heating from room temperature, the ε-Fe2O3nanoparticles’ saturation magnetization undergoes a monotonic decrease while the coercivity and remanence sharply drop, virtually vanishing around ∼500 K. However, above that temperature the hysteresis loops present a nonlinear response with finite coercivity, making evident signs of ferrimagnetic order up to temperatures as high as 850 K (TN1). The neutron diffraction study confirms the presence of ferrimagnetic order well above 500 K with Pna'21' magnetic symmetry, but only involving two of the four Fe3+ sublattices which are ordered below TN2 ≈ 480 K, and with a reduced net ferromagnetic component, that vanishes at above 850 K. The results unambiguously show the presence of a high-temperature magnetic phase in ε-Fe2O3 with a critical temperature of TN1 ∼ 850 K. Importantly, this temperature is similar to the Curie point in other iron oxides, indicating comparable magnetic coupling strengths. The presence of diverse magnetic phases is further supported by the nonmonotonic evolution of the thermal expansion. The existence of a high-temperature ferrimagnetic phase in ε-Fe2O3 may open the door to further expand the working range of this multifunctional iron oxide.

 

 

Hits: 3123
Oxides for new-generation electronics

Unveiling a New High-Temperature Ordered Magnetic Phase in ε-Fe2O3



Also at ICMAB

  • New Sensitive and Selective Chemical Sensors for Ni2+ and Cu2+ Ions: Insights into the Sensing Mechanism through DFT Methods

    Information
    09 April 2021 100 hit(s) Oxides
    We report the synthesis and theoretical study of two new colorimetric chemosensors with special selectivity and sensitivity to Ni2+ and Cu2+ ions over other metal cations in the CH3CN/H2O solution. Compounds (E)-4-((2-nitrophenyl)diazenyl)-N,N-bis(pyridin-2-ylmethyl)aniline (A) and (E)-4-((3-nitrophenyl)diazenyl)-N,N-bis(pyridin-2-ylmethyl)aniline (B) exhibited a drastic color change from yellow to colorless, which allows the detection of the mentioned metal cations through different techniques.
  • Silicon nanowires as acetone-adsorptive media for diabetes diagnosis

    Information
    06 April 2021 200 hit(s) Oxides
    Early detection of diabetes, a worldwide health issue, is key for its successful treatment. Acetone is a marker of diabetes, and efficient, non-invasive detection can be achieved with the use of nanotechnology. In this paper we investigate the effect of acetone adsorption on the electronic properties of silicon nanowires (SiNWs) by means of density functional theory.
  • Soft‐Chemistry‐Assisted On‐Chip Integration of Nanostructured α‐Quartz Microelectromechanical System

    Information
    30 March 2021 171 hit(s) Oxides
    The development of advanced piezoelectric α‐quartz microelectromechanical system (MEMS) for sensing and precise frequency control applications requires the nanostructuration and on‐chip integration of this material on silicon material.
  • Critical Effect of Bottom Electrode on Ferroelectricity of Epitaxial Hf0.5Zr0.5O2 Thin Films

    Information
    26 March 2021 198 hit(s) Oxides
    Epitaxial orthorhombic Hf0.5Zr0.5O2 (HZO) films on La0.67Sr0.33MnO3 (LSMO) electrodes show robust ferroelectricity, with high polarization, endurance and retention. However, no similar results have been achieved using other perovskite electrodes so far. Here, LSMO and other perovskite electrodes are compared.
  • Metallic Diluted Dimerization in VO2 Tweeds

    Information
    19 March 2021 217 hit(s) Oxides
    Though first order transitions are thought to be abrupt, materials find cunning ways to smooth the jump. Here we show that VO2 chooses making beautiful tapestries at the atomic scale. To see how, and how they affect its intriguing metal-insulator transition, continue reading:

INSTITUT DE CIÈNCIA DE MATERIALS DE BARCELONA, Copyright © 2020 ICMAB-CSIC | Privacy Policy | This email address is being protected from spambots. You need JavaScript enabled to view it.