ELECTRIC-FIELD CONTROL OF GIANT MAGNETORESISTANCE IN SPIN-VALVES SYED RIZWAN * ,† , H. F. LIU * and X. F. HAN * ,‡,§ * Institute of Physics, Chinese Academy of Sciences Beijing 100190, P. R. China † Department of Physics, CIIT Islamabad, Pakistan ‡ xfhan@aphy.iphy.ac.cn SEN ZHANG and Y. G. ZHAO ¶ Department of Physics, Tsinghua University Beijing 100084, P. R. China ¶ ygzhao@tsinghua.edu.cn S. ZHANG Department of Physics, University of Arizona Tucson, Arizona 85721, USA zhangs@physics.arizona.edu Received 8 November 2011 Accepted 17 February 2012 Published It has been known that magnetic properties of a ferromagnet grown on piezoelectric substrates can be altered by the electric ¯eld-induced strain. We consider spin-valve CoFe/Cu/CoFe/IrMn grown on (011)-cut piezoelectric Pb(Mg 1=3 Nb 2=3 ÞO 3 PbTiO 3 (PMNPT) substrate and inves- tigate the e®ect of the electric ¯eld on the giant magnetoresistance (GMR) of the spin valve. We found that the electric ¯eld induced strain on PMNPT substrate enhances the coercivity of the magnetic layers. The transport measurement shows that the GMR ratio of the spin valve could be altered as much as 50% for an electric ¯eld of 8 kV/cm. The change of GMR is attributed to the reduced maximum degree of the antiparallel alignment between the magnetization directions of the free and pinned layers. The present studies establish a prototype electrically tunable magnetic memory device such that the electric ¯eld can reversibly tune spin valve magnetoresistance without deteriorating electric and magnetic properties. Keywords : Converse piezoelectric e®ect; giant magnetoresistance; spin-valve; superconducting quantum interference device. 1. Introduction A spin valve consisting of two ferromagnetic layers separated by a nonmagnetic layer (metal or insulator) is an essential element in today's hard disk drive (HDD) reading heads and magnetic random access memories (MRAM). The working principle of the § Corresponding author. SPIN Vol. 2, No. 1 (2012) 1250006 (6 pages) © World Scienti¯c Publishing Company DOI: 10.1142/S2010324712500063 March 29, 2012 12:15:13pm WSPC/273-SPIN 1250006 ISSN: 2010-3247 FA1 1250006-1