Spin-Dependent Tunneling between a Soft Ferromagnetic Layer and Hard Magnetic Nanosize Particles

Abstract

Spin-dependent tunneling has been investigated for ferromagnetic tunnel junctions with a new structure, which consists of a hard ferromagnetic insulating granular thin film sandwiched between two soft ferromagnetic layers, or soft ferromagnetic and non-ferromagnetic layers. The granular film, consisting of ferromagnetic Co 80 Pt 20 nanosize particles embedded in a SiO 2 matrix with 13 nm thickness, has a high coercive force. The film was prepared by co-sputtering of Co 80 Pt 20 and SiO 2 targets on a glass substrate with a Cr or a Co 80 Pt 20 /Fe underlayer as a bottom electrode. A ferromagnetic Co 9 Fe layer as a top electrode was deposited over the granular film to form cross pattern junctions of 0.01 mm 2 junction area through a metal mask. The tunneling magnetoresistance up to 4.5% at RT was observed for a Co 9 Fe/Co 80 Pt 20 –SiO 2 /Co 80 Pt 20 /Fe junction at a low field.