Ráðstefnugreinar - HÍConvention papershttps://hdl.handle.net/20.500.11815/7142024-03-19T11:06:16Z2024-03-19T11:06:16ZPhotoluminescence study of Si<sub>1-x</sub>Ge<sub>x</sub> nanoparticles in various oxide matricesSultan, Muhammad TahaGudmundsson, J. T.Manolescu, AndreiCiurea, Magdalena LidiaSvavarsson, HalldorIngvarsson, Snorrihttps://hdl.handle.net/20.500.11815/39482023-02-09T08:33:31Z2021-10-06T00:00:00ZPhotoluminescence study of Si<sub>1-x</sub>Ge<sub>x</sub> nanoparticles in various oxide matrices
Sultan, Muhammad Taha; Gudmundsson, J. T.; Manolescu, Andrei; Ciurea, Magdalena Lidia; Svavarsson, Halldor; Ingvarsson, Snorri
We investigate the photoluminescence properties of structures comprising of Si1-xGex nanoparticles (NPs) within SiO2, GeO2, TiO2 and Ta2O5 oxide matrices. Of the investigated structures, it was observed that the structures with GeO2 and TiO2 matrices provide increased spectral response (at ~907 and 844 nm respectively) and increased PL intensity. The improved PL characteristic have been attributed to increased diffusion barrier against oxygen which otherwise would result in formation of unwanted oxide at the film-oxide interface, thereby deteriorating the optical properties.
2021-10-06T00:00:00ZEffect of VN buffer layer on the magnetic anisotropy of epitaxial Ni<sub>80</sub>Fe<sub>20</sub>thin films deposited on MgO (001) substratesSultan, Muhammad TahaTryggvason, ÁsgeirArnalds, UnnarIngvarsson, Snorrihttps://hdl.handle.net/20.500.11815/39302023-01-30T14:40:50Z2022-10-12T00:00:00ZEffect of VN buffer layer on the magnetic anisotropy of epitaxial Ni<sub>80</sub>Fe<sub>20</sub>thin films deposited on MgO (001) substrates
Sultan, Muhammad Taha; Tryggvason, Ásgeir; Arnalds, Unnar; Ingvarsson, Snorri
This study incorporates the structural and magnetic characterization of epitaxial Ni80Fe20 films grown by direct current magnetron sputtering on MgO(001) and MgO(001)||VN(001) substrates. A series of samples grown with different N2 flow settings for the deposition of VN and similar permalloy deposition parameters was utilized to investigate the effect of morphological evolution and buffer layer induced strain on the magnetic properties of Ni80Fe20. X-ray diffraction analysis reveals an epitaxial nature of the VN(001) and Py(001) films grown on MgO substrates. Angular dependent magneto-optical Kerr effect characterization reveals a cubic anisotropy for Ni80Fe20 on MgO with a coercivity of ∼0.8 Gauss along the easy directions. Incorporating an epitaxial VN buffer, the structures showed a transition from a cubic to isotropic magneto-crystalline anisotropy with coercivity varying from 2.5 to 25 Gauss for Ni80Fe20 deposition on VN (with N2 varying from 5 to 12 sccm). The variation is attributed to the microstructural evolution of the Ni80Fe20 to 3D structures along with an induced structural strain.
2022-10-12T00:00:00ZStructural and magnetic changes in CoAlZr thin films upon post annealingTryggvason, ÁsgeirFrímannsdóttir, T. H.Sultan, Muhammad TahaThorarinsdottir, K. A.Magnus, F.Ingvarsson, Snorrihttps://hdl.handle.net/20.500.11815/39292023-01-30T14:45:38Z2022-10-12T00:00:00ZStructural and magnetic changes in CoAlZr thin films upon post annealing
Tryggvason, Ásgeir; Frímannsdóttir, T. H.; Sultan, Muhammad Taha; Thorarinsdottir, K. A.; Magnus, F.; Ingvarsson, Snorri
We present a study of the effect of
annealing amorphous ferromagnetic thin films of
Co0.85(Al0.7Zr0.3)0.15, post deposition. The annealing was
done in vacuum with no applied magnetic field. We find
that already at a relatively low annealing temperature
of 130 ◦C there is crystallite formation that introduces
both structural and magnetic inhomogeneity. This does not
affect the saturation magnetization strongly, but strongly
affects the switching behavior and the overall effective
anisotropy of the films. Further, there is a dramatic
increase in magnetization damping. Thus, the annealing
has a profound effect on both static and dynamic magnetic
properties of the material. This is important to keep in
mind for potential applications using these materials.
2022-10-12T00:00:00ZStrong ground motion in the epicentral area of the 2020-2021 earthquake swarm in the Reykjanes Peninsula, IcelandHernandez, VictorRupakhety, RajeshÓlafsson, SímonBessason, BjarniErlingsson, Sigurdurhttps://hdl.handle.net/20.500.11815/38382023-01-10T10:49:14Z2022-09-04T00:00:00ZStrong ground motion in the epicentral area of the 2020-2021 earthquake swarm in the Reykjanes Peninsula, Iceland
Hernandez, Victor; Rupakhety, Rajesh; Ólafsson, Símon; Bessason, Bjarni; Erlingsson, Sigurdur
The Geldingadalur eruption in the Reykjanes Peninsula on 19 March 2021 was
preceded by several earthquakes of volcano-tectonic origin throughout 2020 and 2021.
Seven earthquakes with magnitude M≥5 took place during the swarm, all of them recorded by the Icelandic Strong Motion Network operated by the Earthquake Engineering Research Centre of the University of Iceland. In this paper we present salient features of strong ground motion in the epicentral area caused by the swarm. Interestingly, earthquakes as small as M5.0 caused peak ground acceleration (PGA) larger than the 475-year return period PGA at a town near the epicentral area. At two recording stations, unusually high energy content at vibration periods <0.3s was detected, with spectral accelerations exceeding the design values. The largest recorded horizontal PGA was ~0.4g at Krýsuvík, station, which is the strongest PGA recorded in Iceland since the MW6.3 2008 Ölfus Earthquake. For this station we present horizontal-to-vertical spectral ratios indicating likely site-effects. We also compare the attenuation of PGA of the largest event of the sequence with two groundmotion prediction equations (GMPEs). The recorded PGA attenuation is well captured by a local GMPE.
2022-09-04T00:00:00Z