Regensburg 2007 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 15: Poster:ThinFilms(1-33),Transp.(34-49),ExchBias(50-56),
Spindynamics(57-70),Micro-nanostr.Mat.(71-82),
Particles/Clust.(83-88), Mag.Imag./Surface(89-96),
Spinelectronics(97-109), Theory/Micromag.(110-116),
Spinstruct/Phasetr.(117-128),Magn.Mat.(129-139),
Aniso.+Measuring(140-145), MolMag.(146-152),
MSMA(153-156)

MA 15.50: Poster

Dienstag, 27. März 2007, 15:00–19:00, Poster A

A study on the influence of nano-oxide layer on magnetotransport properties of NiMn based giant magnetoresistive spin valve sensors — Anoop Gupta¹, •Senthilnathan Mohanan¹, Ulrich Herr¹, Zaoli Zhang², and Ute Kaiser² — ¹Institute for Micro and Nanomaterials, University of Ulm, Ulm-89081, Germany — ²Electron Microscopy Group of Material Science, University of Ulm, Ulm-89069, Germany

NiMn with L1o structure is one of the good antiferromagnetic materials that can be used for exchange bias in giant magnetoresistive spin valve (GMR-SV) sensors. However, as-deposited NiMn exists in FCC phase which exhibits paramagnetic behaviour. So it has to be annealed at around 300°C in order to achieve FCC to FCT structural phase transformation. Annealing leads to interdiffusion, but this can be controlled by using a nano-oxide layer (NOL). The main aim of this study is to investigate the influence of NOL on the magnetotransport and the structural properties of NiMn/Co/Cu/Co GMR-SV sensors. An increase in the GMR has been observed with the inclusion of NOL in the pinned layer, which is due to the reduced diffusion of Ni and Mn on to the GMR active region. However, we observed a decrease in exchange bias field of the pinned Co layer. A detailed investigation of the influence of the position of NOL in the pinned layer on exchange bias and magnetotransport properties has been done. The optimum position for the NOL is found to be in the middle of the pinned Co layer. The structural phase transformation of NiMn upon annealing has been studied using x-ray diffractometer and HR-TEM.