| With the development of spintronics, the composite systems of magnetic metal (Fe, Co, Ni, Mn, etc) and semiconductor (Si, GaAs, Ge, etc), which were paid a lot of attentions, present attracting properties, such as in-plane anisotropy, the enhanced Hall coefficient, negative temperature coefficient of resistivity etc. The Hall sensitivity of Fe-Ge composite systems can reach 82 V/AT, indicating a promising application in Hall detectors, but the mechanism for the enhancement is still under discussion. In literature, the research on Fe-Ge composite systems focused mainly on the coupling between the magnetic metals, and more studies on their transport properties are needed.Fe/Ge multilayers and Fe/Ge discontinuous multilayers were fabricated by magnetron sputtering. Structure, composition and properties such as magnetic properties, resistivity, magneto-resistivity and Hall effect were studied systematically. Structure characterization indicates a periodic modulated structure with alternately deposited polycrystalline Fe and amorphous Ge layers of Fe/Ge multilayers. The room-temperature magnetic measurement reveals the uniaxial magnetic anisotropy of Fe/Ge multilayers with the uniaxial anisotropy Ku=2.27×103 J/m3. The temperature coefficient of resistivity of all the films is positive at room temperature but turns to be negative at low temperatures due to the weak localization effect. The Fe/Ge multilayers show anomalous Hall effect and the Hall sensitivity KH is independent of the temperature. When the periodΛis 5.2 nm, the anomalous Hall coefficient Rs reaches its largest value of 1.8×10-7 m/T, which is three orders of magnitude larger than that of bulk Fe material.With the increase of Fe content, the Fe in Fe/Ge discontinuous multilayers has a trend to be crystalline and Ge is amorphous. Magnetic measurement indicates the antiferromagnetic coupling between Fe particles and the maximum saturated magnetization reaches 1400 emu/cc. A tunneling conductive mechanism is revealed when the content of Fe is lower than 0.6, but a metallic conductive mechanism presents at large Fe contents. The temperature induced change of the saturated Hall resistance becomes small with the increase of Fe content, and the largest Hall oefficient Rs reaches 9.6×10-8 m/T. After being annealed, the Fe in the Fe/Ge multilayers alloys with Ge and the saturated magnetization reduces. The transport properties are metallic, and the anomalous Hall effect disappears. With the increase of temperature, the sign of the Hall coefficient changes from negative to positive.
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