arXiv subjects

R. Magaraggia

Publications and source records attributed to R. Magaraggia.

6 recordsLinked to original sources

arXiv2011

Interfacial coupling across a modified interface studied with ferromagnetic resonance

Using spin waves we directly probe the interface of an exchange biased Ni$_{80}$Fe$_{20}$/Ir$_{25}$Mn$_{75}$ film which has been modified by the presence of an Au dusting layer. Combining this experimental data with a discretised simulation model, parameters relating to interface exchange coupling and modification of interface magnetisation are determined. Exchange coupling is found to be relatively uniform as gold thickness is increased, and undergoes a sudden drop at 1.5$\textrmÅ$ of gold. Interface magnetisation decreases as a function of the gold dusting thickness. Antiparallel alignment of the ferromagnet and antiferromagnet supress the interface magnetisation compared to when they are in parallel alignment. These findings imply that the interface region has specific magnetisation states which depend on the ferromagnet orientation.

cond-mat.mes-hall↗

arXiv2010

Probing La(0.7)Sr(0.3)MnO3 multilayers via spin wave resonances

La(0.7)Sr(0.3)MnO3/BiFeO3 and La(0.7)Sr(0.3)MnO3/PbZr20Ti80O3 epitaxial heterostructures have been grown on SrTiO3 substrates. Spin wave resonances are used to study interface properties of the ferromagnetic La(0.7)Sr(0.3)MnO3. We find that the addition of the BiFeO3 or PbZr20Ti80O3 causes out-of-plane surface pinning of the La(0.7)Sr(0.3)MnO3. We are able to place new limits on the exchange constant D of La(0.7)Sr(0.3)MnO3 grown on these substrates and confirm the presence of uniaxial and biaxial anisotropies caused by the SrTiO3 substrate.

cond-mat.mtrl-sci↗

arXiv2010

Magnetization pinning in conducting films demonstrated using broadband ferromagnetic resonance

The broadband microstrip ferromagnetic resonance technique has been applied for detection and characterization of a magnetic inhomogeneity in a film sample. In the case of a 100nm thick Permalloy film an additional magnetically depleted top sub-layer, practically unidentifiable by the conventional ferromagnetic resonance setup, has been detected and characterized. These results have been confirmed by Brillouin light scattering spectroscopy revealing the fact that the optical properties of the additional sub-layer do not differ much from those of the bulk of the film. Subsequent characterization of a large number of other presumably single-layer films with thicknesses in the range 30-100nm using the same ferromagnetic resonance technique also revealed the same effect.

cond-mat.mtrl-sci↗

arXiv2010

Dynamic pinning at a Py/Co interface measured using inductive magnetometry

Broadband FMR responses for metallic single-layer and bi-layer magnetic films with total thicknesses smaller than the microwave magnetic skin depth have been studied. Two different types of microwave transducers were used to excite and detect magnetization precession: a narrow coplanar waveguide and a wide microstrip line. Both transducers show efficient excitation of higher-order standing spin wave modes. The ratio of amplitudes of the first standing spin wave to the fundamental resonant mode is independent of frequency for single films. In contrast, we find a strong variation of the amplitudes with frequency for bi-layers and the ratio is strongly dependent on the ordering of layers with respect to a stripline transducer. Most importantly, cavity FMR measurements on the same samples show considerably weaker amplitudes for the standing spin waves. All experimental data are consistent with expected effects due to screening by eddy currents in films with thicknesses below the microwave magnetic skin depth. Finally, conditions for observing eddy current effects in different types of experiments are critically examined.

cond-mat.mtrl-sci↗

arXiv2009

Microwave screening by conduction currents in thin magnetic films: application in stripline broadband FMR

Ferromagnetic resonance in conducting magnetic bilayers was studied using microstrip transducers. It was found that excitation or suppression of standing spin waves could be achieved through enhanced inhomogeneity of eddy currents in the bilayer caused by finite thickness. This effect is observable in films with thicknesses below the magnetic skin depth and can be used to study standing spin wave modes in heterostructures.

cond-mat.mtrl-sci↗

arXiv2008

Self-organized plane arrays of metallic magnetic elements

We studied the dynamic magnetic properties of plane periodical arrays of circular permalloy nano-dots fabricated using a self-organized mask formed by polysterene nanospheres on the surface of a Permalloy film. Conventional (microwave cavity) and broadband coplanar-line ferromagnetic resonance setups were used for the measurements. We found several well resolved resonance peaks. This result shows that the self-organized mask fabrication technique is able to produce high-quality samples with small dispersion of geometrical and magnetic parameters.

cond-mat.mtrl-sci↗