Remnant X-ray Magnetic Circular Dichroism Investigation of the Local Magnetic Contributions to the Magnetization of a Coercive Bimetallic Molecule-Based Magnet

Abstract

X-ray magnetic circular dichroism (XMCD) measurements have been performed at the Cr and Fe K-edges for the two-dimensional oxalate-based magnet {[N(C 4 H 9 ) 4 ][Fe II Fe III 0.77 Cr III 0,23 (oxin its long-range ordered magnetic state. First, the XMCD spectra recorded under a 2 T applied magnetic field are used to probe the local exchange interaction between the metal ions through the relative orientation of their spins in the magnetic field. The remnant local magnetic moments on the Cr and Fe ions have been clearly evidenced, analyzed, and compared to the total remnant magnetization measured by conventional magnetometry. The respective impact of single ion anisotropy, magneto-structural anisotropy, and exchange interaction on the remnant magnetic state is then discussed.

A cookbook for the investigation of coordination polymers by transition metal K-edge XMCD

“…As for temperature, the effect related to the different values of the magnetic field described here is purely related to the measurements conditions, since all the measurements are performed below the Curie temperature and so in the same magnetic ordering state. Nevertheless, it is interesting to point out that XMCD measurements at different magnetic field can also bring valuable information on the investigated compound (Train et al, 2004;Bartolome ´et al, 2005;Osawa et al, 2007;Boada et al, 2010b;Chaboy et al, 2010;Guglieri et al, 2012;Koumousi, 2015;Jafri, 2016;Lahiri et al, 2016;Platunov et al, 2019;Pajerowski et al, 2020). Finally, our goal here was to optimize the value of the applied magnetic field for our PBAs but not to perform element-selective magnetic hysteresis from XMCD; these measurements require either the direction of the magnetic field to be fixed and the helicity of the photons switched (Pizzini et al, 1997), or to apply an appropriate procedure if the helicity cannot be switched.…”

“…Additionally, XMCD retains the chemical sensitivity of X-ray absorption spectroscopy (XAS), which is priceless when two or more TMs are present. Many kinds of compounds could thus be investigated and their properties better understood, for instance oxides (Subías et al, 2009;Ramos et al, 2009), alloys (Dartyge et al, 1995), magnetic multilayers (Pizzini et al, 1995), intermetallic compounds (Boada et al, 2010a), molecular magnets (Train et al, 2004) or Prussian blue analogs (PBAs) (Verdaguer et al, 1995(Verdaguer et al, , 1999Dujardin et al, 1998;Champion et al, 2001;Cafun et al, 2013;Lahiri et al, 2016). All these results were obtained thanks to worldwideavailable beamlines allowing for TM K-edge XMCD measurements, using either a scanning setup (Rogalev & Wilhelm, 2015;Haskel et al, 2007;Nakamura & Suzuki, 2013;Poldi et al, 2020) 1 or a dispersive one, for instance on ODE (Baudelet et al, 2011(Baudelet et al, , 2016 at SOLEIL (France), ID24 ISSN 1600-5775 (Mathon et al, 2004;Pascarelli et al, 2016) at ESRF, EDXAS (Cezar et al, 2010) at LNLS (Brazil), or BL-08 (Patra et al, 2019) at Indus-2 (India).…”

The fruitful introduction of chirality and control of absolute configurations in molecular magnets

“…Nevertheless, the overall magnetisation remains weak, a factor which is not favourable for the observation of strong MCh effects for example. The authors have proposed two means to bypass the limitation brought about by the AF nature of the exchange interaction: (i) a proper choice of the metal ions to favour F exchange interaction; 45 this strategy partly failed because of the AF dipolar coupling of the F-coupled 2D layers; (ii) a statistical mixing of the metal ions towards ferrimagnets; 44 this strategy is very classical in solid state chemistry and had been extended to molecule-based materials; [48][49][50][51][52] its efficiency and limitations have been demonstrated.…”

Interplay between Transition-Metal K-edge XMCD and Magnetism in Prussian Blue Analogs

“…Most of the works on TM K-edges in the literature deal with the investigation of metal oxides and especially metals, metal alloys, and intermetallics, − the electronic properties of which are well described in terms of the band structure. Works dealing with molecular compounds, in which the electrons are localized and the electronic properties are well described in terms of molecular orbitals, are scarcer. − And yet, molecular orbital approaches have proved fruitful to describe and anticipate some electronic properties of molecular compounds. Our work belongs within this kind of less developed approach and invites us to take a fresh look at this long-standing issue.…”