In this letter, magnetization reversal is investigated in (Ga,Mn)As thin films using the magneto-optical Kerr effect. A Stoner–Wohlfart model, modified to take into account the existence of magnetic reversal discontinuities associated with nucleation and propagation phenomena allows us to estimate most of the characteristic constants. These results demonstrate a reversal behavior analogous to that observed in metallic magnetic layers (coherent rotation followed by a nucleation propagation process). The dynamic study at T=20 K shows a strong increase of the coercivity with the increase of dH/dt. This effect is related to the random distribution of Mn magnetic ions in the lattice.

We have investigated reactively sputtered films of RuO2 for possible application in very large scale integrated circuits. Sputtering yields stoichiometric ruthenium dioxide in a large window of oxygen pressures and the films are reasonably low stressed in the 10−9 dyn cm−2 range. The resistivity of as deposited films is 40 μΩ cm. The films are excellent barriers against interdiffusion of Si and Al.

We have prepared controlled arrays of submicron permalloy particles as part of a program to determine the magnetic properties of verifiable single-domain particles (SDP) and the effects of interactions between SDPs. We have measured the hysteresis loops of these arrays as a function of size, aspect ratio, and spacing. The arrays are fabricated utilizing electron beam lithography and liftoff techniques. Each array consists of approximately 106 identical particles with identical spacing between the particles. Particle size and spacing [center-to-center distance (ccd)], vary from 5 μm×15 μm (width by length) with ccd of 25 μm to 0.07 μm×0.1 μm with ccd of 0.25 μm. The thickness of the films varied from 0.072 to 0.049 μm. Hysteresis loops are obtained utilizing a SQUID magnetometer. For well-separated particles we observe an order of magnitude increase in Hc with decreasing particle size, and then a subsequent decrease in Hc as the ccd is reduced. However, even for the smallest particles, the ratio of the remanence to saturation magnetization indicates that they are not single domain, and the loop shape is not indicative of Stoner–Wohlfarth behavior.

We report on the structure and characterization of the major phase in the Bi-Sr-Ca-Cu-0 system that becomes superconducting below 80 K. A superlattice modulation in the structure that is incommensurate with a tetragonal perovskite-based subcell is observed using electron diffraction. High-resolution imaging indicates that the modulation occurs primarily in bismuth-rich layers in the structure.