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Register a new userHow Gold nanoparticle acquires magnetism? - Formation of large orbital moment at the interface
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In this paper, we have tried to find out the origin of magnetism in Gold nanoparticles (Au- NPs). We observe that upon incorporating Gold nanoparticles (Au-NPs) in Fe3O4 nanoparticle medium the net magnetisation increases compared to the pure Fe3O4 nanoparticle medium. This increase of magnetization can be attributed to the large orbital magnetic moment formation at the Au/magnetic particle interface indicating that magnetism observed in Au-NPs is an interfacial effect. This interfacial effect has been supported by the observation of sudden transition from positive saturated magnetisation to a negative diamagnetic contribution as a function of magnetic field on citrate coated gold Au-NPs.
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We demonstrate an organic memory-transistor device based on a pentacene-gold nanoparticles active layer. Gold (Au) nanoparticles are immobilized on the gate dielectric (silicon dioxide) of a pentacene transistor by an amino-terminated self-assembled monolayer. Under the application of writing and erasing pulses on the gate, large threshold voltage shift (22 V) and on/off drain current ratio of ~3E4 are obtained. The hole field-effect mobility of the transistor is similar in the on and off states (less than a factor 2). Charge retention times up to 4500 s are observed. The memory effect is mainly attributed to the Au nanoparticles.
Nanoscale step structures have attracted recent interest owing to their importance in both fundamental and applied research, for example in adsorption, in catalysis, and in directing nanowire growth. Here, we used a template-stripping method to obtain vicinal-like surface structures on grains of polycrystalline gold and investigated the effect of annealing temperature on the formation of these surfaces.
We report electronic structure calculations of an iron impurity in gold host. The spin, orbital and dipole magnetic moments were investigated using the LDA+$U$ correlated band theory. We show that the {em around-mean-field}-LDA+$U$ reproduces the XMCD experimental data well and does not lead to formation of a large orbital moment on the Fe atom. Furthermore, exact diagonalization of the multi-orbital Anderson impurity model with the full Coulomb interaction matrix and the spin-orbit coupling is performed in order to estimate the spin Hall angle. The obtained value $gamma_S approx 0.025$ suggests that there is no giant extrinsic spin Hall effect due to scattering on iron impurities in gold.
In this paper we study the possible relation between the electronic and magnetic structure of the TiO2/LaAlO3 interface and the unexpected magnetism found in undoped TiO2 films grown on LaAlO$_3$. We concentrate on the role played by structural relaxation and interfacial oxygen vacancies. LaAlO3 has a layered structure along the (001) direction with alternating LaO and AlO2 planes, with nominal charges of +1 and -1, respectively. As a consequence of that, an oxygen deficient TiO2 film with anatase structure will grow preferently on the AlO2 surface layer. We have therefore performed ab-initio calculations for superlattices with TiO2/AlO2 interfaces with interfacial oxygen vacancies. Our main results are that vacancies lead to a change in the valence state of neighbour Ti atoms but not necessarily to a magnetic solution and that the appearance of magnetism depends also on structural details, such as second neighbor positions. These results are obtained using both the LSDA and LSDA+U approximations.
The signature of magnetism without a ferromagnet in a non-magnetic heterostructure is novel as well as fascinating from fundamental research point of view. It has been shown by AlMari et al: that magnetism can be induced at the interface of Cu/C60 due to change in density of states. However, the quantification of such interfacial magnetic moment has not been performed yet. In order to quantify the induced magnetic moment in Cu, we have performed X-ray magnetic circular dichroism (XMCD) measurements on Cu/C$_{60}$ multilayers. We have observed room temperature ferromagnetism in Cu/C$_{60}$ stack. Further XMCD measurements show that ~0.01 $mu_B$/atom magnetic moment has been induced in Cu at the Cu/C$_{60}$ interface.
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