The distribution of switching fields (Hsw) in a NiFe wire was investigated as a function of temperature between 5 and 300 K. The sample structure under investigation is Ta/NiFe/Cu/NiFe wire (150 nm width) connecting to a square pad (large area) at an end. Magnetization reversal phenomena are very sensitively detected using the giant magnetoresistance effect. With repeating magnetoresistance measurements, we obtained a histogram of Hsw with three narrow peaks at each temperature. The origin of three peaks can be attributed to the existence of three different kinds of magnetic domain structures at the pad area, which was confirmed by magnetic force microscopy observation.
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