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AM: Magnetismus

AM 10: Postersitzung

AM 10.43: Poster

Tuesday, March 23, 1999, 16:15–20:00, F\"urstenberghaus

Designing and Testing of Sensors from Polycrystalline Perovskite Manganites — •Y. Xu, V. Dworak, A. Drechsler, S. Lukas, and U. Hartmann — Institute of Experimental Physics, University of Saarbrücken, D-66041 Saarbrücken, Germany

Sensors from bulk La_0.67Sr_0.33MnO₃ and La_0.67Ba_0.33MnO₃ have been successfully fabricated with a special low cost and easy fabrication technique. Magnetoresistance (MR) ratios of the sensors as large as 20 % at 77 K and 1.2 % at room temperature were observed under fields of 700 Oe. Corresponding field sensitivities as high as 6 ohm per Tesla at 3 mT and 298 K, and 12-15 ohm per Tesla at 3 - 8 mT and 77 K were obtained. The sensors exhibit stability and long life time as needed for common use. It is found that the high-field MR is independent of the field orientation. This is attributed to field-induced suppression of spin fluctuations in contiguous grains. The very large low-field MR, however, is strongly anisotropic in three field orientations with respect to the current. This phenomenon is associated with intergranular transport of spin-polarized electrons and is discussed in terms of spin-polarized tunneling through two different groups of grain boundaries.