Electrochemically Induced Strain Evolution in Pt-Ni Alloy Nanoparticles Observed by Bragg Coherent Diffraction Imaging.

Strain is known to enhance the activity of the oxygen reduction reaction in catalytic platinum alloy nanoparticles, whose inactivity is the primary impediment to efficient fuel cells and metal-air batteries. Bragg coherent diffraction imaging (BCDI) was employed to reveal the strain evolution during the voltammetric cycling in Pt-Ni alloy nanoparticles composed of PtNi, PtNi, and PtNi. Analysis of the 3D strain images using a core-shell model shows that the strain as large as 5% is induced on Pt-rich shells due to Ni dissolution.

Controlling the Transverse Magneto-Optical Kerr Effect in Cr/NiFe Bilayer Thin Films by Changing the Thicknesses of the Cr Layer.

Here, we demonstrate the impact of ferromagnetic layer coating on controlling the magneto-optical response. We found that the transverse magneto-optical Kerr effect (TMOKE) signal and TMOKE hysteresis loops of NiFe thin layers coated with a Cr layer show a strong dependence on the thickness of the Cr layer and the incidence angle of the light. The transmission and reflection spectra were measured over a range of incidence angles and with different wavelengths so as to determine the layers' optical parameters and to explain the TMOKE behavior.