Journal of Magnetism and Magnetic Materials 263 (2003) 57–71 Magnetic and structural characteristics of exchange biasing systems based on NiMn antiferromagnetic films S. Groudeva-Zotova* ,1 , D. Elefant, R. Kaltofen, D. Tietjen, J. Thomas, V. Hoffmann, C.M. Schneider Leibniz Institute of Solid State Physics, Helmholtzstr. 20, IFF-IFW-Dresden, Dresden D-01069, Germany Received 9 May 2002; received in revised form 19 November 2002 Abstract We have investigated the magnetic and the structural characteristics of bi-layer exchange biasing (EB) systems NiMn–Coasfunctionoftheantiferromagnetic(AFM)filmdepositionparametersandofthepost-depositionannealing andfield-coolingprocedures.Theeffectsofsputteringpressure,growthrate,seedlayerandoftheannealingparameters were studied by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM) and Magneto-Optical Kerr (MOKE) effect measurements. The results yielded optimised deposition conditions and permitted us to establish efficient annealing and field-cooling procedures. The best obtained EB systems with 5nm Co film reveal coercive field H c X35Oeandexchangebiasfield H EB X95Oeandhavegoodstabilityinairuptoatleast2001C. Theobtainedmagneticcharacteristicsarecloselycorrelatedwiththecrystallinestructureoftheas-depositedsamples and with the phase transformation effects. According to our results, the as-deposited samples are a mixture of a non- equilibrium FCC NiMn phase (quenched by the sputtering deposition process) and a variable amount of the equilibriumfacecentredtetragonal(FCT)phase.Theratioofthesetwophasesdependsonthedepositionconditions— theamountoftheFCTNiMnphaseislargerifdepositionconditionsclosertoequilibriumhavebeenused,especiallyat higher sputtering gas pressure and higher deposition rates. The annealed samples contain dominantly the FCT AFM phase as confirmed by XRD and TEM-diffraction analyses. The transition to this AFM state depends on the initial structure of the as-grown samples and, respectively, on their deposition conditions. r 2002 Elsevier Science B.V. All rights reserved. PACS: 68.55.a; 75.50.Ee; 75.70.i Keywords: NiMn; AFM–FM bi-layers; Field cooling; Exchange bias; Crystalline structure 1. Introduction Bi-layer exchange biasing (EB) systems invol- ving antiferromagnetic (AFM) and ferromagnetic (FM) layers are important elements in spin valves used in GMR sensors and reading heads. Optimisingtheircrystallinestructureandmagnetic *Corresponding author. Tel.: +3514659641; fax: +3514659745. E-mail address: s.zotova@ifw-dresden.de (S. Groudeva-Zotova). 1 OnleaveofabsencefromtheInstituteofElectronics,BAS, Sofia, Bulgaria. 0304-8853/03/$-see front matter r 2002 Elsevier Science B.V. All rights reserved. doi:10.1016/S0304-8853(02)01535-4