FRINK Linked Data Fragments server

Matches in SemOpenAlex for { <https://semopenalex.org/work/W2734854601> ?p ?o ?g. }

• W2734854601 abstract "Broad study of magnetic properties of YIG films is performed. This thesis covers the whole path from YIG sample growth to characterization of magnetization dynamics. In the sub-chapter 5.1, full magnetic characterization of the thin sputtered YIG films is given. A batch of YIG samples with thicknesses of 19, 29, 38 and 49 nanometer is grown by magnetron sputtering for the spin waves experiment. The thickness and the surface roughness are controlled by XRR and AFM measurements. The obtained sample thickness differs by the value of about 1 nm from the planed sample thickness which means that the growth process is well established. Saturation magnetization of the samples is measured by SQUID. The value for the thickest 49 nm sample is 163 mT which is very close to the bulk value (175 mT). With decrease of the sample thickness the saturation magnetization drops up to 99 mT for 19 nm sample. We performed the FMR measurements of the samples to determine the Gilbert damping parameter. The Gilbert damping is 0.00024 for 49 nm sample and grows up to 0.0008 for 19 nm sample. Such dependence of the damping on the sample thickness is typical for the systems were two magnon scattering is a dominant relaxation mechanism. These values of damping are bigger than the values of the Gilbert damping reported in the literature for the samples grown by PLD and LPE techniques. Dependence of the resonance frequency on the resonance field is measured to determine the effective magnetization and subsequently to calculate the anisotropy constant. Our samples possess rather large out-of plane anisotropy which is the evidence of a good crystalline structure. Despite large Gilbert damping the samples are proper for spin waves measurements. In sub-chapter 5.2 results of the spin wave measurements are provided. We performed TR-MOKE imaging of the spin waves in thin YIG films and extracted the mode structure of the spin waves. For quasi single mode excitation we were able to fit the SW decay with a damped oscillator function providing us with information about the attenuation length in the thin YIG film structures for the first spin wave mode. MUMAX simulations were performed to compare experimental and simulated modes. The MOKE data is in a very good agreement with these simulations. The physical origin of long propagating „edge modes“ is revealed during the measurements. The reason is the microwave current flowing in Ti/Au capping of the YIG film. This current is excited inductively by the CPW. Measurements of the spin wave attenuation length showed that the spin waves propagate as if the Gilbert damping is much higher (α ≈ 0.002) than measured for pure YIG. This occurs due to the presence of the spin pumping at the YIG/Ti interface. To check this, comparative measurements of spin wave propagation on stripes capped with Ti/Au and Aluminum are performed. For Al capped films the decay length increases by roughly a factor of 2. These results make sense since the spin pumping should much smaller for such light metal as Al. To make a double check of this hypothesis the separate measurements of the spin pumping at the YIG/Ti interface were performed. We measured the Gilbert damping on the YIG/Ti, YIG/AlOx/Ti, YIG/Au and YIG/AlOx/Au samples with FMR technique. Enhanced Gilbert damping with the value α = 0.0021 is observed only in case of YIG/Ti interface. This confirms our hypothesis about the spin pumping. We calculated the spin-mixing conductance for YIG/Ti films. Obtained value is 4.1∗1017 m-2 which is approximately three times smaller than for YIG/Pt interfaces.We also studied the dependence of the Kerr signal on the thickness of the reflecting capping layer on top of the YIG film to find the optimal thickness for MOKE experiments. The optimal thickness lies in range between 6 and 10 nm. The unexpected result is that we are able to see the spin waves through rather thick (about 40 nm) Au layer. The question arises whether we probe directly the spin waves in YIG film with the laser through a thick metal layer, or it is a spin accumulation signal in Au layer created by the spin pumping from YIG film. This might become an object of the further study.In sub-chapter 5.4 results of the spin Hall measurements are provided. Dependence of the FMR linewidth on the applied current has a form of asymmetric parabola. This is due to heating effects caused by the current running through the Pt films. Unfortunately, GGG substrate is a very bad heat sink which makes direct observation of the linear, spin Hall - based contribution rather difficult. Nevertheless we are able to extract linear part from parabolic dependence which is proportional to the spin Hall angle. For 30 nm YIG sample with 12 nm evaporated Pt film the value for the spin Hall angle is 0.026. The reason why the measured value is small is a very low interface transparency (T= 0.18). The intrinsic spin Hall angle is 0.141 correspondingly. This result is consistent with the values reported in literature. To improve the interface transparency we studied spin pumping of Pt films grown by different methods. MBE grown Pt turned out to be the best choice since it shows the largest spin pumping. For 30 nm YIG sample with 9 nm of MBE grown Pt the value of the spin Hall angle is 0.088. The interface transparency is indeed larger (0.57) and the value of the intrinsic spin Hall angle is 0.152. As expected the intrinsic value of the spin Hall angle is approximately the same for both experiments. The attempt was made to reduce the heating by switching to the pulsed mode. Unfortunately, the MOKE experimental setup does not allow us to work with pulse duty cycle larger than 10. The pulsed mode measurements show that heat contribution still has a dominant influence on FMR linewidth. The SHE effect measurements gave us correct values for the spin Hall angle. Unfortunately, they also showed that the sputtered YIG on GGG can not be considered as a candidate for auto oscillations measurements due to its large Gilbert damping and accumulation of the heat in the area of the current flow. In sub-chapter 5.6 we show results measured with microwave cavity on thick LPE grown YIG. The cavity method gives accurate results only in the approach of weak electromagnetic field perturbation inside of the cavity. In our case the sample volume was to large, which made the accurate calculation of the spin Hall angle impossible. Nevertheless the observed effect is definitely tailored to the spin Hall angle. The cavity measurements showed that for very big (≈ 104) current pulse duty cycles the heating effect is negligibly small. They also showed that the heat that changes the FMR linewidth is accumulated on the large time scale (> 50 µs). The current pulse width is 50 µs and there is no measurable heating influence on the damping." @default.
• W2734854601 created "2017-07-21" @default.
• W2734854601 creator A5045236577 @default.
• W2734854601 date "2017-07-07" @default.
• W2734854601 modified "2023-10-16" @default.
• W2734854601 title "Dynamical measurements of the Spin Hall angle" @default.
• W2734854601 hasPublicationYear "2017" @default.
• W2734854601 type Work @default.
• W2734854601 sameAs 2734854601 @default.
• W2734854601 citedByCount "0" @default.
• W2734854601 crossrefType "dissertation" @default.
• W2734854601 hasAuthorship W2734854601A5045236577 @default.
• W2734854601 hasConcept C121332964 @default.
• W2734854601 hasConcept C147120987 @default.
• W2734854601 hasConcept C155194400 @default.
• W2734854601 hasConcept C21690051 @default.
• W2734854601 hasConcept C26873012 @default.
• W2734854601 hasConcept C42704618 @default.
• W2734854601 hasConcept C62520636 @default.
• W2734854601 hasConcept C97355855 @default.
• W2734854601 hasConceptScore W2734854601C121332964 @default.
• W2734854601 hasConceptScore W2734854601C147120987 @default.
• W2734854601 hasConceptScore W2734854601C155194400 @default.
• W2734854601 hasConceptScore W2734854601C21690051 @default.
• W2734854601 hasConceptScore W2734854601C26873012 @default.
• W2734854601 hasConceptScore W2734854601C42704618 @default.
• W2734854601 hasConceptScore W2734854601C62520636 @default.
• W2734854601 hasConceptScore W2734854601C97355855 @default.
• W2734854601 hasLocation W27348546011 @default.
• W2734854601 hasOpenAccess W2734854601 @default.
• W2734854601 hasPrimaryLocation W27348546011 @default.
• W2734854601 hasRelatedWork W1990656902 @default.
• W2734854601 hasRelatedWork W2010816611 @default.
• W2734854601 hasRelatedWork W2016301829 @default.
• W2734854601 hasRelatedWork W2034187388 @default.
• W2734854601 hasRelatedWork W2071448458 @default.
• W2734854601 hasRelatedWork W2072842384 @default.
• W2734854601 hasRelatedWork W2330167652 @default.
• W2734854601 hasRelatedWork W2350193355 @default.
• W2734854601 hasRelatedWork W2540288867 @default.
• W2734854601 hasRelatedWork W2565590683 @default.
• W2734854601 hasRelatedWork W2787620649 @default.
• W2734854601 hasRelatedWork W2798756540 @default.
• W2734854601 hasRelatedWork W2896218654 @default.
• W2734854601 hasRelatedWork W2941835711 @default.
• W2734854601 hasRelatedWork W2980512168 @default.
• W2734854601 hasRelatedWork W3102270375 @default.
• W2734854601 hasRelatedWork W3106238286 @default.
• W2734854601 hasRelatedWork W3126214223 @default.
• W2734854601 hasRelatedWork W2926196734 @default.
• W2734854601 hasRelatedWork W2961154327 @default.
• W2734854601 isParatext "false" @default.
• W2734854601 isRetracted "false" @default.
• W2734854601 magId "2734854601" @default.
• W2734854601 workType "dissertation" @default.