Journal of Magnetism and Magnetic Materials 247 (2002) 187–190 Magnetic exchange bias enhancement through seed layer variation in FeMn/NiFe layered structures Lance Ritchie a, *, Xiaoyong Liu a , Snorri Ingvarsson a , Gang Xiao a , Jun Du b , John Q. Xiao b a Physics Department, Brown University, 182 Hope Street, Providence, RI 02912, USA b Physics Department, University of Delaware, Newark, DE 19716, USA Received 30 November 2001 Abstract The exchange bias and crystalline texture of the multilayer structure (Ta/Al/seed/Fe 50 Mn 50 /Ni 81 Fe 19 /Al 2 O 3 / Ni 81 Fe 19 /Al/Ta with seed=Ni 81 Fe 19 or Ni 81 Fe 19 /Cu) has been characterized. Measurements indicate an abrupt decrease in exchange bias of the Ni 81 Fe 19 pinned layer for samples with very thin seed layers, and exchange bias as high as 325 Oe for thicker seed layers. Fluctuation of exchange bias with thickness was greatly reduced for the Ni 81 Fe 19 /Cu seed configuration. X-ray diffraction measurements demonstrate a correlation between exchange bias and strong (1 1 1) texture of FeMn. The results suggest a high sensitivity of Ni 81 Fe 19 roughness and texture on deposition conditions, and corroborate previous observations of roughness in ultrathin NiFe films. r 2002 Elsevier Science B.V. All rights reserved. PACS: 75.30.Gw; 75.70.Cn Keywords: Exchange anisotropy; FeMn; NiFe Magnetic tunnel junction (MTJ) based devices are emerging as the most promising candidates for the future development of magnetic random access memory (MRAM) [1,2] and magnetic sensor applications [2]. Thus, the high-yield fabrication of reliable MTJ structures is becoming an increas- ingly important technical concern. A large ex- change biasing between the pinned ferromagnetic (FM) layer and the antiferromagnetic (AFM) pinning layer promotes magnetic stability of the pinned layer, which is key to the production of reliable, high-quality MTJ structures with de- creased sensitivity to magnetic noise. The exchange biasing of NiFe/FeMn-based systems is known to be highly sensitive to the crystallographic texture [3–5] and interface roughness [6]. The purpose of the present study is to characterize the dependence of exchange bias on seed layer thickness and composition. Two types of MTJ multilayer samples were prepared, both types having the overall structure (Ta 50 ( A/Al 200 ( A/seed/FeMn 120 ( A/Ni 79 Fe 21 60 ( A/Al 2 O 3 14 ( A/Ni 79 Fe 21 120 ( A/Al 200 ( A/Ta 50 ( A). In the present study, layers above the 60 ( A NiFe pinned layer are inconsequential. The inclu- sion of these layers was intended only to allow for subsequent patterning of the multilayer samples *Corresponding author. E-mail address: ritchie@physics.brown.edu (L. Ritchie). 0304-8853/02/$-see front matter r 2002 Elsevier Science B.V. All rights reserved. PII:S0304-8853(02)00156-7