Local magnetoresistive response in thin-film Ni-Fe read elements: a sub-micrometer-resolution measurement system

Bulk and local magnetoresistive responses in Ni-Fe thin films were measured as a function of applied magnetic field and field angle. The measurements were made using a four-probe resistance measurement system, which consisted of two scanning microprobes for voltage taps, each less than 1 mu m in tip diameter. The scanning resolution of the microprobes was 0.5 mu m. The system was used to determine domain formation and motion in magnetoresistive read heads. Longitudinal fields, produced by demagnetizing or external field components, may cause domain formation and subsequent domain-wall motion (and annihilation). This leads to Barkhausen noise, which is detrimental to the performance of the device as a magnetic read head. Experimental results for both the bulk and local responses were in qualitative agreement with micromagnetic theory.<
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