Showing papers by "Andrzej Maziewski published in 2003"

Drastic changes of the domain size in an ultrathin magnetic film

Abstract: A general framework for the domain size in any ultrathin film with perpendicular magnetic anisotropy is here discussed. The domain structure is analyzed by using the classical theory taking into consideration the demagnetization field contribution to the domain wall energy. A sinusoidal model is considered to describe the domain structure while approaching, in two different cases, the monodomain state with in-plane magnetization. The first case is realized applying a large enough in-plane magnetic field. The second one is obtained by decreasing the perpendicular magnetic anisotropy, which is connected in many ultrathin systems with the increase of film thickness. A change in the domain size of several orders of magnitude is obtained while approaching the magnetization reorientation region. The minimal stripe domain period p=8πlex2/d is calculated from the sinusoidal model, where lex is the exchange length and d is the thickness of the film. The range of possible domain size changes in ultrathin films is p...

Magnetic ordering in ultrathin cobalt film covered by an overlayer of noble metals

Abstract: The spatial distribution of magnetic properties studied by polar Kerr-effect-based magnetometry are carried out on an ultrathin cobalt wedge covered with a silver wedge whose slopes are perpendicular to each other and subsequently capped with a gold layer. The coercivity field was studied as a function of both cobalt thickness d and silver thickness h. A few monolayers of Ag were found to have a substantial influence on the coercivity field. A similar strong influence of silver coverage on the magnetic anisotropy field was observed. Domain structure evolution during magnetization reversal is investigated using an optical microscope. With an increase of the magnetic field, a magnetization reversal process occurs: first by domain nucleation and next by a domain wall movement towards the higher coercivity region of the sample. Changes of the fractal dimension of the domain wall as well as nucleation center density are investigated. A rapid increase of these parameters is observed while d increases towards the value of spin reorientation transition, which goes from easy-axis to easy-plane magnetization. Similar strong changes were observed while decreasing d to the lowest thickness available for observation. The problem discussed here, of tuning magnetic properties by silver–gold structure, is important from both a general physics and an application point of view, especially because of the possibilities for magnetic film patterning.

Magnetooptical micromagnetometry of ultrathin Co wedge in Au/Co/Au structures

Abstract: Ultrathin cobalt wedges Au/Co(0 < d < 2 nm)/Au(111)/Mo/Al 2 0 3 , grown by molecular beam epitaxy, were investigated by means of the polar Kerr effect. Coercivity field H c as a function of Co film thickness d was determined from the hysteresis loops. Domain structure in the remnant states, affected by a magnetic history of the sample, were investigated by optical polarizing microscope equipped with a computer controlled CCD camera. Both domain nucleation center maximum density, n max (d) registered during magnetization reversal process and wall fractal dimension, f d (d), were determined by digital images processing. Increasing d, a rapid increase of both n max and f d was observed approaching the magnetization reorientation phase transition from easy axis into easy plane. Similar strong changes were observed while decreasing d for the lowest thickness available for observation.