Wheatstone bridges incorporating a serially connected ensemble of simple AMR elements of Ni 80 Fe 20 film were produced, targeting an application of a pinned magnetic field along the sensing magnetoresistor length. For the optimal dimension, the magnetoresistive element with length l ¼ 4 mm, width w ¼ 150 mm and thickness t ¼ 5 nm still shows a rather modest AMR ratio (of about 0.85% only). However, the resulting bridge exhibits a sensitivity as large as 2.15 mV/Oe. This is according to a

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... rd sensitivity of 1.80 mV/V/Oe and a detection limit better than 10 À6 emu, which is almost doubled with respect to that in the typical commercial AMR devices and is comparable with Permalloy based PHE sensor. This is suitable to detect the superparamagnetic fluid of 50 nm-Fe 3 O 4 -chitosan.