Properties of the manganese-based single-molecule magnet [Mn(6)(III)Cr(III)](3+) are studied. It contains six Mn(III) ions arranged in two bowl-shaped trinuclear triplesalen building blocks linked by a hexacyanochromate and exhibits a large spin ground state of S(t) = 21/2. The dominant structures in the electron emission spectra of [Mn(6)(III)Cr(III)](3+) resonantly excited at the L(3)-edge are the L(3)M(2, 3)M(2, 3), L(3)M(2, 3)V and L(3)VV Auger emission groups following the decay of the primary p(3/2) core hole state. Significant differences of the Auger spectra from intact and degraded [Mn(6)(III)Cr(III)](3+) show up. First measurements of the electron spin polarization in the L(3)M(2, 3)V and L(3)VV Auger emission peaks from the manganese constituents in [Mn(6)(III)Cr(III)](3+) resonantly excited at the L(3)-edge near 640 eV by circularly polarized synchrotron radiation are reported. In addition spin resolved Auger electron spectra of the reference substances MnO, Mn(2)O(3) and Mn(II)(acetate)(2)·4H(2)O are given. The applicability of spin resolved electron spectroscopy for characterizing magnetic states of constituent atoms compared to magnetic circular dichroism (MCD) is verified: the spin polarization obtained from Mn(II)(acetate)(2)·4H(2)O at room temperature in the paramagnetic state compares to the MCD asymmetry revealed for a star-shaped molecule with a Mn(4)(II)O(6) core at 5 K in an external magnetic field of 5 T.
3+ structural type adsorbed thin films prepared on Si and gold-coated glass substrates have been experimentally studied by means of spin-polarized electron spectroscopy (SPES) and X-ray magnetic circular dichroism (XMCD) at the Fe L 3,2 edge using circularly-polarized synchrotron radiation. The results are cross-compared to the corresponding data obtained from the recently published measurements with Mn-based SMM [1], also in terms of the local spin and orbital magnetic moments obtained. Furthermore, [Fe III 6 Cr III ] 3+ single crystals have been experimentally studied by means of magnetometry and X-ray diffraction.
The usage of double pinned magnetic CoFeB/MgO/CoFeB tunnel junctions with noncollinear magnetizations as sensors of mechanical stress is shown. For this purpose, tunnel magnetoresistive (TMR) stacks with MnIr based pinning of both electrodes have been prepared. By using different MnIr thicknesses, we were able to realize noncollinear magnetizations. A series of annealing steps with a field perpendicular to the initial exchange bias direction have been performed in order to find the optimum thermal treatment for the best performance of the sensors. On these systems, bending experiments were completed which, show the suitability of our double-pinned TMR elements as stress sensors and their performance in differentiating tensile and compressive stress.
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Single-molecule magnets (SMM) of the [Mn III 6 Cr III ] 3+ structural type prepared on Si and gold-coated glass substrates have been investigated by spin-resolved electron spectroscopy (SPES) and X-ray magnetic circular dichroism (XMCD) at the Mn L 3,2 edge and in addition by XMCD at the Cr L 3,2 edge using synchrotron radiation. Differences between the two methods are discussed. Despite its severe limitations for 3d transition metals, a spin sum rule evaluation is nevertheless performed for the Mn III centres in the [Mn III 6 Cr III ] 3+ SMM to provide a simple means of comparing XMCD and spin-resolved electron spectroscopy results.
We investigated the structural, magnetic, and electrical properties of the perpendicularly magnetized Mn4-xFexGe thin films (0.3 ≤ x ≤ 1). The tetragonally distorted structure was verified for all investigated stoichiometries. High coercive fields in the range of 1.61 T to 3.64 T at room temperature were measured and showed increasing behavior with decreasing Fe content. The magnetic moments range from (0.16 ± 0.02) μB/f.u for Mn3Fe1Ge to (0.08 ± 0.01) μB/f.u for Mn3.4Fe0.6Ge. X-ray absorption spectroscopy revealed ferromagnetic coupling of the Mn and Fe atoms in Mn4-xFexGe and the ferrimagnetic ordering of the Mn magnetic moments. Anomalous Hall effect measurements showed sharp magnetization switching. The resistivity values are in the range of 207 μΩ cm to 457 μΩ cm depending on the stoichiometry. From the contribution of the ordinary Hall effect in the anomalous Hall effect measurements, Hall constants, the charge carrier density, and mobility were deduced. The thermal conductivity was calculated using the Wiedemann-Franz law. All these values are strongly influenced by the stoichiometry. An alternative method was introduced for the determination of perpendicular magnetic anisotropy. The values range between 0.26 MJ/m3 and 0.36 MJ/m3.
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