Reversed magnetic anisotropy of (100) Pd/Ni/Pd and Pd/NiPd/Pd structures: Effects of changing lattice mismatch

Abstract

(100) oriented Pd/Ni/Pd and Pd/NiPd(80/20)/Pd films have been deposited on (100) Si using epitaxial Cu and Pd seed layers. Keeping the two Pd layers at 1000 Å each and varying the Ni and NiPd layer thickness, a completely reversed magnetic anisotropy is observed for the 25 Å Ni layer and 50 Å NiPd layer. A squared hysteresis loop is seen for the normal-to-plane magnetization curves of these structures, with a little loop for the in-plane curves. A partially reversed anisotropy is seen for the Pd/Ni/Pd structure with a 50 Å Ni layer. For the structures with thicker Ni layers, a much easier magnetization is seen for the in-plane curves. The reversed anisotropy is attributed to the stress on the thin Ni and NiPd layers by the cladding Pd layers. Identical Pd/Ni/Pd and Pd/NiPd/Pd structures with an (111) orientation, deposited on (111) Si with (111) Cu seed layers, show no sign of changing magnetic anisotropy. Comparison with the results on the (100) Cu/Ni/Cu structures provides evidence of the effect of changing lattice mismatch on the thickness of Ni and NiPd needed for the occurrence of a reversed magnetic anisotropy.