Iermolenko V. Optical, magnetic and transport properties of Heusler alloys and heterostructures based on them.

The search of new Heusler alloys perspective for practical application in spintronic devises as spin injectors has been performed. The correctness of the results of ab-initio calculations of electronic structure of alloys has been checked by the comparison of their experimental and calculated optical properties. The effect of atomic disorder on the electronic structure and some physical (magnetic, transport and optical) properties of some Heusler alloys has been investigated. It was shown that Co2CrGa is ferromagnet with significant (Р = 87,7 %) degree of spin polarization of free charge carriers. This fact makes this alloy perspective for practical applications in spintronic devises. The nature of structural instability of Fe2MnGa has been investigated. It was established that L21 type of structure with ferrimagnetic type of magnetic order (Р = 73,8 %) is less energetically favorable than Cu3Au type of structure and ferromagnetic type of magnetic order (Р = 8,7 %), while the difference in full energies between these states consists of 60 meV only. Unlike the case of Co2CrAl Heusler alloy films the atomic disorder L21?В2 in Co2Cr0.6Fe0.4Al alloy films practically does not change the magnetization and spin polarization degree, while B2?А2 type of disorder noticeable reduces the spin polarization degree of alloy. The relaxation and plasma frequencies of free charge carriers of Cu-Mn-Al alloy in austenite and martensite states have been evaluated from the analyses of the optical properties of alloy. The knowledge of these parameters allowed us to explain the nature of the resistivity changes induced by the martensitic transformation in alloy. The composition dependencies of magnetoresistive and transport properties of granular (FeCo)x(MgO)1-x films on ferromagnetic fraction (FeCo) has been established.