Structure, Magnetic And Transport Properties Of Fe₃Si Heusler Alloy Films

Heusler alloys have received great attentions due to their high spin polarization andhigh Curie temperature for potential spintronic applications. Fe3Si, which can be writtenasFe II Fe I21Si, is a binary X2YZ type Heusler alloy. In this thesis, polycrystalline andepitaxial Fe3Si films were fabricated by sputtering, and their structure, magnetic andtransport properties were investigated experimentally.Polycrystalline Fe3Si films with high structural quality can be grown on Sisubstrates at500oC. The resistivity of the polycrystalline Fe3Si films obeysunconventional single–magnon scattering mechanism and electron–phonon scatteringmechanism at low and high temperatures, respectively. The anomalous Hall resistanceincreases linearly with the applied magnetic field below12kOe and reaches saturationat high fields, which is similar to the M–H curves measured out of plane. The plane Hallresistance shows sine wave relation with the angle in plane.Polycrystalline Fe3Si films were also grown on MgO(001) substrates in differenttemperature. The Fe3Si film fabricated at300oC shows T12(T <100K)relationship due to the weak localization effect and the anomalous Hall effect followsskew scattering mechanism. However the Fe3Si films obtained at400,600and700oCshow T3(T <100K) unconventional one–magnon scattering mechanism, and boththe skew scattering and side–jump mechanism are involved in the anomalous Halleffect.Fe3Si films with (001),(112) and (011) c–axis orientations were grown bycosputtering on MgO(001),(011) and (111) substrates at500oC, respectively. Theepitaxial relationship of the Fe3Si films on MgO was verified by X–ray diffractions withθ–2θ, tilting and φ scans. All the planar Hall resistance curves of the Fe3Si films withdifferent orientations show a nearly sinusoidal behavior at high fields. When themagnetic field is below100Oe, the lineshapes of planar Hall effect of the Fe3Si(001)and Fe3Si(112) films deviate from the sin2Mfunction and show an abrupt switching.Meanwhile, the curves of planar Hall effect of the Fe3Si(011) film show triangle shape.The planar Hall effect at high fields can be fitted by single domain magnetic momentreversal model. The different low–field planar Hall effects in the Fe3Si films can beexplained by multi–domain magnetic properties and different in–plane epitaxial which are closely correlated to the relation between the in–plane symmetries of thefilms and substrates.The Fe3Si(111) film were epitaxially grown on Ge(111) substrates. The film showsbrassica oleracea like morphology, which is different from the epitaxial films on MgOsubstrates. Fe3Si/Ge(111) shows weak rectifying behavior due to interfacialinterdiffusion and/or interaction.