Anomalous magnetic behavior in half-metallic Heusler Co2FeSi alloy glass-coated microwires with high Curie temperature

In the current study, we have succeeded to fabricate Co2FeSi Heusler alloy glass-covered microwires with magnetic core nucleus diameter d = 4.36 mu m and total diameter D = 17.55 mu m, with high Curie temperature (T-e > 1100 K) and well-defined magnetic anisotropy for high temperature spintronic devices application. The magnetic properties of as-prepared and annealed at different temperature (873 K, 973 K and 1073 K for 1 h) of Co2FeSi Heusler alloy glass-covered microwires have been investigated. Strong dependence of the magnetic properties on the annealing conditions has been indicated. Anomalous magnetic behavior for annealed samples at 873 K and 973 K has been found and structural properties of such samples have been analyzed. Critical temperatures 155 K and 250 K have been detected for annealed samples at 873 K and 973 K, respectively, where the behavior of M-H loops and coercivity changed. Below the critical point the M -H curve shows "kink or wasp-waisted" magnetic behavior and complex magnetic reversal mechanism is supposed. The anomalous magnetic behavior is due to the martensitic phases induced by annealing con-ditions below the room temperature. This unusual magnetization behavior provides opportunities to un-derstand the phenomena of different types of magnetic domain structures in the preferred crystallographically oriented Co2FeSi Heusler alloy glass-coated micro-wires, essentially helpful for de-signing the devices based on magnetization switching.