اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدIron porphyrin molecules on Cu(001): Influence of adlayers and ligands on the magnetic properties
122
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
The structural and magnetic properties of Fe octaethylporphyrin (OEP) molecules on Cu(001) have been investigated by means of density functional theory (DFT) methods and X-ray absorption spectroscopy. The molecules have been adsorbed on the bare metal surface and on an oxygen-covered surface, which shows a $sqrt{2}times2sqrt{2}R45^{circ}$ reconstruction. In order to allow for a direct comparison between magnetic moments obtained from sum-rule analysis and DFT we calculate the dipolar term $7< T_z>$, which is also important in view of the magnetic anisotropy of the molecule. The measured X-ray magnetic circular dichroism shows a strong dependence on the photon incidence angle, which we could relate to a huge value of $7< T_z>$, e.g. on Cu(001) $7< T_z>$ amounts to -2.07,mbo{} for normal incidence leading to a reduction of the effective spin moment $m_s + 7< T_z>$. Calculations have also been performed to study the influence of possible ligands such as Cl and O atoms on the magnetic properties of the molecule and the interaction between molecule and surface, because the experimental spectra display a clear dependence on the ligand, which is used to stabilize the molecule in the gas phase. Both types of ligands weaken the hybridization between surface and porphyrin molecule and change the magnetic spin state of the molecule, but the changes in the X-ray absorption are clearly related to residual Cl ligands.
قيم البحث
اقرأ أيضاً
We present a detailed ab initio study of the electronic structure and magnetic order of an Fe monolayer on the Ir(001) surface covered by adsorbed oxygen and hydrogen. The results are compared to the clean Fe/Ir(001) system, where recent intensive st
udies indicated a strong tendency towards an antiferromagnetic order and complex magnetic structures. The adsorption of an oxygen overlayer significantly increases interlayer distance between the Fe layer and the Ir substrate, while the effect of hydrogen is much weaker. We show that the adsorption of oxygen (and also of hydrogen) leads to a p(2$times $1) antiferromagnetic order of the Fe moments, which is also supported by an investigation based on a disordered local moment state. Simulated scanning tunneling images using the simple Tersoff-Hamann model hint that the proposed p(2$times $1) antiferromagnetic order could be detected even by non-magnetic tips.
Graphene is expected to complement todays Si-based information technology. In particular, magnetic molecules in contact with graphene constitute a tantalizing approach towards organic spin electronics because of the reduced conductivity mismatch at t
he interface. In such a system a bit is represented by a single molecular magnetic moment, which must be stabilized against thermal fluctuations. Here, we show in a combined experimental and theoretical study that the moments of paramagnetic Co-octaethylporphyrin (CoOEP) molecules on graphene can be aligned by a remarkable antiferromagnetic coupling to a Ni substrate underneath the graphene. This coupling is mediated via the pi electronic system of graphene, while no covalent bonds between the molecule and the substrate are established.
Growth, electronic and magnetic properties of $gamma$-Fe$_{4}$N atomic layers on Cu(001) are studied by scanning tunneling microscopy/spectroscopy and x-ray absorption spectroscopy/magnetic circular dichroism. A continuous film of ordered trilayer $g
amma$-Fe$_{4}$N is obtained by Fe deposition under N$_{2}$ atmosphere onto monolayer Fe$_{2}$N/Cu(001), while the repetition of a bombardment with 0.5 keV N$^{+}$ ions during growth cycles results in imperfect bilayer $gamma$-Fe$_{4}$N. The increase in the sample thickness causes the change of the surface electronic structure, as well as the enhancement in the spin magnetic moment of Fe atoms reaching $sim$ 1.4 $mu_{mathrm B}$/atom in the trilayer sample. The observed thickness-dependent properties of the system are well interpreted by layer-resolved density of states calculated using first principles, which demonstrates the strongly layer-dependent electronic states within each surface, subsurface, and interfacial plane of the $gamma$-Fe$_{4}$N atomic layers on Cu(001).
We present ab-initio calculations of the magnetic moments and magnetic anisotropy energies of small FeCo clusters of varying composition on top of a Cu(100) substrate. Three different cluster layouts have been considered, namely 2x2, 3x3 and cross-li
ke pentamer clusters. The ratio of Co atoms with respect to the total number in a chosen cluster (``concentration) was varied and all possible arrangements of the atomic species were taken into account. Calculations have been performed fully relativistically using the embedded cluster technique in conjunction with the screened Korringa-Kohn-Rostoker method and the magnetocrysergy depend on the position they occupy in a particular cluster and on the type and the number of nearest-neighbors. The MAE for the 2x2 and 3x3 clusters varies with respect to the ``concentration of Co atoms in the same manner as the corresponding monolayer case, whereas the pentamer clusters show a slightly different behavior. Furthermore, for the clusters with an easy axis along a direction in the surface plane, the MAE shows a significant angular dependence.
High-quality and impurity-free magnetite surfaces with (sqrt2xsqrt2)R45o reconstruction have been obtained for the Fe3O4(001) epitaxial films deposited on Fe(001). Based on atomically resolved STM images for both negative and positive sample polarity
and Density Functional Theory calculations, a model of the magnetite (001) surface terminated with Fe ions forming dimers on the reconstructed (sqrt2xsqrt2)R45o octahedral iron layer is proposed.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
