Giant magnetoresistance in half metallic Fe3 O4 based spin valve structures

Abstract

A systematic study of the magnetic and in-plane magnetotransport properties of Fe3 O4 Cu Ni80 Fe20 spin valve structures is presented. We observed that the spin valve structure is highly sensitive to the thickness of the Cu spacer layer tCu. For tCu =2 nm, the structure exhibits a clear anisotropic magnetoresistance at low magnetic fields but no giant magnetoresistance (GMR) effect due to strong exchange coupling between the Fe3 O4 and Ni80 Fe20 layers. In contrast, a positive GMR effect is measured for tCu 5 nm due to separate magnetization switching of the Fe3 O4 and Ni80 Fe20 layers. We have also investigated that the temperature dependence of the GMR effect observed marked changes at low temperatures. © 2007 American Institute of Physics.