Magnetization pinning in conducting films demonstrated using broadband ferromagnetic resonance

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 amplitud…

Coplanar waveguide based ferromagnetic resonance in ultrathin film magnetic nanostructures: impact of conducting layers

We report broadband ferromagnetic resonance (FMR) measurements based on a coplanar waveguide (CPW) of ultrathin magnetic film structures that comprise in-plane/out-of-plane decoupled layers deposited on nonmagnetic buffer layers of various thickness or other buffer structures with a diverse sheet resistance. We show that the excitation of the fundamental mode can be substantially (up to 10 times) enhanced in the structures deposited on buffer layers with a low sheet resistance in comparison to the structures deposited on thin or weakly conducting buffer layers. The results are analyzed in term…

Theoretical study of the stripline ferromagnetic resonance response of metallic ferromagnetic films based on an analytical model

We develop an advanced analytical model for calculating the broadband stripline ferromagnetic resonance (FMR) response for metallic ferromagnetic films, taking into account the exchange interaction as well as the exchange boundary conditions at the film surface. This approach leads to simple analytical expressions in the Fourier space. As a result, a numerical code which implements inverse Fourier transform of these equations is very quick. This allows us to explore a wide space of parameters as numerical examples of application of this theory. In particular, we investigate the joint effect of…

Critical currents and vortex dynamics in super-conducting MgB2

The recently-discovered MgB2 super-conductor has a transition temperature Tc approaching 40K, placing it intermediate between the families of low and high temperature super-conductors (LTS and HTS). In practical applications, super-conductors are permeated by quantised magnetic flux vortices, and when a current flows there is dissipation unless the vortices are "pinned" in some way, and so inhibited from moving under the influence of the Lorentz force. This vortex motion sets the limiting critical current density Jc in the super-conductor. Vortex behaviour has proved to be more complicated in …

Metallicity in Ultra-Thin Oxygen-Deficient SrTiO$_3$ Thin Films

We report on the observation of metallic behavior in thin films of oxygen-deficient SrTiO$_3$ - down to 9 unit cells - when coherently strained on (001) SrTiO$_3$ or DyScO$_3$-buffered (001) SrTiO$_3$ substrates. These films have carrier concentrations of up to 2$\times10^{22}$ cm$^{-3}$ and mobilities of up to 19,000 cm$^2$/V-s at 2 K. There exists a non-conducting layer in our SrTiO$_{3-δ}$ films that is larger in films with lower carrier concentrations. This non-conducting layer can be attributed to a surface depletion layer due to a Fermi level pinning potential. The depletion width, trans…

原子层沉积生长的氧化锌与掺铝氧化锌薄膜中的三次谐波产生及光致发光测量

Third Harmonic Generation And Photoluminescence Measurements in Zinc Oxide And Aluminum doped Zinc Oxide Thin Films Grown by Atomic Layer Deposition

本文实验研究原子层沉积掺铝氧化锌薄膜的禁带、波长依赖三次谐波与单光子光致发光，发现最高4%弱掺杂可使三阶非线性响应较未掺杂样品数倍增强。

锑掺杂对SmFeAs(O,F)超导性能的影响

Antimony Doping Effect on the Superconducting Properties of SmFeAs(O,F)

本研究合成不同锑掺杂量的SmFeAs(O,F)块体，发现锑掺杂会增大晶格参数、降低超导转变温度与临界电流密度，且该行为与铈、镧基同类1111体系的锑掺杂效应不同。