Magnetic and transport properties of granular and Heusler-type glass-coated microwires

We studied magnetic and structural properties of granular CoxCu100-x (5 < x < 40 at%), Cu63Fe37 and Heusler-type Ni2MnGa glass-coated microwires. We found that the structure of Co-Cu microwires consists of two phases: fcc Cu for all the samples and fcc alpha-Co present for higher Co content. In the case of low Co content, Co atoms are distributed within the Cu matrix. The quantity and the size of grains strongly depend on the geometry of the microwire. Co-Cu and Fe-Cu microwires exhibited considerable magnetoresistance (MR). For CoxCu100-x microwires at x >= 30 the anisotropic contribution to MR has been observed. Temperature dependences of magnetization measured without an external magnetic field (ZFC) and in the presence of a field (FC) show considerable difference below 20 K, indicating the presence of small alpha-Fe or Co grains embedded in the Cu matrix. Annealed Ni2MnGa microwires showed ferromagnetic behavior with Curie temperature about 330 K and polycrystalline structure with space group I4/mmm and lattice parameters a=3.75 angstrom and c=6.78 angstrom. (C) 2012 Elsevier BY. All rights reserved.