Preisach analysis of reversible magnetization in SmCo/Fe films

Abstract

SmCo(50 nm)/Fe(y nm) bilayers (y=0, 2.5, 5, 20) were prepared by magnetron sputtering on Si substrates. The films showed coercivities in the range 1.5–14 kOe as well as remanence enhancement, characteristic of exchange-coupled systems. Henkel plots for these bilayers showed that the demagnetizing interactions increase as the thickness of the Fe layer increases. For each film, a set of minor loops was measured in order to determine the Preisach distributions. With suitable analytic forms for these distributions, we obtained a description of the experimental data for the major loops, the minor loops and recoil curves. The comparison with experiment is excellent. From the moving Preisach model we have determined the evolution of the reversible and irreversible magnetization components during the magnetization and demagnetization processes. The most important source of Mrev is the reversible rotation of the magnetization in the grains of the SmCo layer. The soft Fe layer, when well coupled to the SmCo layer, contributes mainly to Mrev, but is also an important source of Mirr.