Effect of target power and composition on RE–Fe–B thin films with Cu and Nb buffer and cap layers

Abstract

We report a systematic study of the structural, morphological, and magnetic properties of RE–Fe–B (RE=rareearth) films codeposited onto thermally oxidized Si substrates. The use of Cu and Nb buffer and cap layers was investigated. The deposition of the samples was performed by magnetron sputtering with the substrates held at 470°C and using various Fe target power densities and fixed RE:Fe:B target power density. This was done in order to vary the growth rate and the Fe content of the films. The simultaneous increase of the deposition rate and Fe content influenced the c-axis texturing of the samples. For the Cu∕RE:Fe:B∕Cu films, as a consequence of the good perpendicular intrinisic coercivity (∼492kA∕m at 10W) and very high remanent polarization (∼1.51T at 110W), very good perpendicular energy products were obtained at 10W (∼133kJ∕m3) and 110W (∼136kJ∕m3). The Nb∕RE:Fe:B∕Nb samples had the best combination of perpendicular energy product and intrinsic coercivity, with values of 150kJ∕m3 and 800kA∕m, respectively, for an iron target power of 20W. This high energy product was retained up to target powers of 50W in spite of the intrinsic coercivity decreasing rapidly with increasing power beyond 20W, because of a marked increase in remanent polarization.