We present measurements of the magnitude of Néel “orange-peel” coupling due to interface roughness in a series of magnetic tunneling junction devices. Results from magnetometry and transport measurements are shown to be in good agreement with the theoretical model of Néel. In addition, we have used transmission electron microscopy to directly probe the sample interface roughness and obtain results consistent with the values obtained by magnetometry and transport methods.

We have observed low-frequency noise due to quasiequilibrium thermal magnetization fluctuations in micron-scale magnetic tunnel junctions (MTJs). This strongly field-dependent magnetic noise occurs within the magnetic hysteresis loops, either as $1/f$ or Lorentzian (random telegraph) noise. We attribute it to the thermally excited hopping of magnetic domain walls between pinning sites. Our results show that magnetic stability is a crucial factor in reducing the low-frequency noise in small MTJs.

We have fabricated single crystal chromium dioxide $\left({\mathrm{CrO}}_2\right)$ films using chemical vapor deposition with chromyl chloride $\left({\mathrm{CrO}}_2{\mathrm{Cl}}_2\right)$ as a liquid precursor. Their electrical and magnetic properties have been investigated. These films are atomically smooth with a rms roughness of less than 5 Å for 1000 Å thick films. We have obtained a spin polarization of $P=98.4\%,$ as determined by the technique of point-contact Andreev reflection. Magnetization and resistivity measurements on these films are in good agreement with those measured on films made with the ${\mathrm{CrO}}_3$ solid precursor. The process using the liquid precursor is superior to other existing techniques for the preparation of single crystal single- and multilayers containing ${\mathrm{CrO}}_2,$ especially the structure of magnetic tunnel junctions.

We observe a strong correlation between magnetization relaxation and electrical resistivity in thin Permalloy $({\mathrm{Ni}}_{81}{\mathrm{Fe}}_{19},$ “Py”) films. Electron scattering rates in the films were affected by varying film thickness and deposition conditions. This shows that the magnetization relaxation mechanism is analogous to “bulk” relaxation, where phonon scattering in bulk is replaced by surface and defect scattering in thin films. Another interesting finding is the increased magnetization damping with Pt layers adjacent to the Py films. This is attributed to the strong spin-orbit coupling in Pt, resulting in spin-flip scattering of electrons that enter from the Py.

The effect of ionization fraction on the epitaxial growth of Cu film on Cu (111) substrate at room temperature is explored. Three deposition methods, thermal evaporation, dc magnetron sputtering (dcMS), and high power impulse magnetron sputtering (HiPIMS) are compared. Three deposition conditions, i.e., fully neutral, 50% ionized, and 100% ionized flux were considered thermal evaporation, dcMS, and HiPIMS, respectively, for ∼20000 adatoms. It is shown that higher ionization fraction of the deposition flux leads to smoother surfaces by two major mechanisms, i.e., decreasing clustering in the vapor phase and bicollision of high energy ions at the film surface. The bicollision event consists of local amorphization which fills the gaps between islands followed by crystallization due to secondary collisions. The bicollision events are found to be very important to prevent island growth to become dominant and increase the surface roughness. Regardless of the deposition method, epitaxial Cu thin films suffer from stacking fault areas (twin boundaries) in agreement with recent experimental results. Thermal evaporation and dcMS deposition present negligible interface mixing while HiPIMS deposition presents considerable interface mixing.