Studies of Fe–Cu microwires with nanogranular structure^*

We report on the fabrication, and structural and magnetic characterization of Cu₆₃Fe₃₇ microwires with granular structure produced by rapid quenching, using the Tailor–Ulitovsky method, from the immiscible alloys. X-ray diffraction study demonstrated that the structure consists of small (6–45 nm) crystallites of Cu and body centred cubic α-Fe. Magnetic properties have been measured in the range of 5–300 K using a SQUID (superconducting quantum interference device) magnetometer. The temperature dependences of the magnetization measured in a cooling regime when no external magnetic field is applied (zero-field cooling) and in the presence of the field (field cooling) show considerable difference below 20 K. This difference could be related to the presence of small α-Fe grains embedded in the Cu matrix. Those α-Fe grains appear to be blocked at temperatures below that at which the maximum of the magnetization is observed in the low temperature range. Significant magnetoresistance (about 7%) has been found in the samples studied. The shape of the observed dependences is typical of a giant magnetoresistance effect.