Narrow Results

Barium ferrite films (BaFe₁₂O₁₉) with perpendicular orientation are attractive candidates for microwave device applications and ultrahigh density perpendicular recording. An in situ annealing process is developed for the deposition of Barium ferrite films by rf magnetron sputtering. The substrates are held at temperatures of 550 to 600°C during the sputtering. After the deposition, the substrate temperature is immediately raised to 900°C in the vacuum chamber in Ar and O₂ atmosphere. c-axis orientated films are obtianed. The films exhibit coercivity value of 4270 Oe and squareness of 0.87 in perpendicular direction.

The phenomenon of domain magnetic shielding by the magnetic sample of external and intrinsic magnetostatic field has been revealed. In this work, we investigate the possibility for detection of the shape and size of magnetic impurity based on the shape of magnetic domain configuration in magnetic film. We show that due to the influence of magnetostatic field of stripe domain structure in magnetic film on the magnetostatic field of magnetic impurity, one can determine the shape and size of this impurity.

Influence of anisotropy on a bending of a magnetic stripe domain wall due to a magnetostatic stray field of a cylindrical magnetic domain (CMD) that is located within the stripe one is under investigation. It is revealed that for a specific set of physical parameters of the domain structure, energy of domain wall bending anisotropy can suppress the bending. An analytical expression for the bending shape is obtained on account of a change of both magnetostatic energy of the configuration and energy of anisotropy of the domain wall.

Magnetic ordering in a mixed domain structure composed of a stripe domain and asymmetrically localized magnetic impurity inside the stripe domain was investigated. The analytical expression for domain walls deformation mediated by the influence of the magnetostatic stray field of the asymmetrically localized magnetic impurity was obtained. The calculations were done for the magnetic film with parameters which are typical for films used in magnetic memory. Experimental implementation of the mixed domain structure composed of the stripe domain and asymmetrically localized magnetic impurity inside the stripe domain was done in (BiLu)₃(FeGa)₅O₁₂ film. Obtained analytical solution for the shape of stripe domain walls distortion is in excellent agreement with the experimental results.

Current perpendicular-to-plane (CPP) magnetoresistance (MR) of La_0.7Ca_0.3MnO₃/LaNiO₃ superlattices sandwiched between two YBa₂Cu₃O₇ thin film electrodes is reported. The CPP-MR in the temperature window of 20 K to 80 K is larger by a factor of 7~15 compared to current-in-plane (CIP) MR. Both CPP and CIP-magnetoresistance decrease with temperature below ~ 20 K. The MR at T<40 K is also strongly hysteretic and does not saturate even at 4 Tesla. Measurements of saturation moment and modeling of the perpendicular-to-plane resistance suggest disorder at the ferromagnetic non-magnetic layer interfaces which dominate the MR. The relative orientation of magnetization in the ferromagnetic layers seems to play only a subservient role in the creation of magnetoresistance.

The growth and structure of ultrathin Rh films on Fe(100) are studied by grazing scattering of 50 keV He projectiles, incident along "random" and low index surface lattice directions. Oscillations in the specular intensity for scattered ions indicate initial layer-by-layer growth, followed by multilayer growth on top of the two-monolayer film. Growth temperatures below about 400 K result in a persistent though rough layer growth up to higher coverages. From distinct maxima in the target current as a function of the azimuthal incidence angle, we deduce that growth is epitaxial and pseudomorphic.