Soft X-ray Magnetic Circular Dichroism in Paramagnetic Systems: Element-Specific Magnetization of Two Heptanuclear CrIII MII6 High-Spin Molecules

The local Ni II and Mn II magnetization was measured in the two paramagnetic high-spin molecules [Cr{(CN)Ni(tetren)} 6 ](ClO 4 ) 9 (intramolecular ferromagnetic coupling) and [Cr{(CN)Mn(TrispicMeen)} 6 ](ClO 4 ) 9 ·3THF (intramolecular antiferromagnetic coupling) by X-ray magnetic circular dichroism (XMCD). The absorption and dichroic spectra were calculated in the ligand field multiplet model to determine the crystal field parameters and the local orientation of the magnetic moments. Local magnetization curves were obtained at the Ni II and Mn II L 2,3 edges for the two molecules. The behavior of the XMCD signals were followed either by varying the magnetic field at T = 20 K or by varying the temperature at H = 6 T. The magnetization vs H or T was compared to spin Hamiltonian calculations including spin−spin exchange and Zeeman effect. The local magnetizations for both Ni II and Mn II ions are not proportional to the macroscopic magnetization. The unique potentiality of XMCD applied to the characterization of exchange-coupled elemental spins in paramagnetic compounds is discussed.