Observation of large Hall sensitivity in thin Fe-Ge amorphous composite films

Amorphous Fex Ge1-x films with different metal volume fractions (0.40<x<1.00) and film thicknesses 4-300 nm were fabricated by a cosputtering method. Magnetic and magnetotransport measurements indicated that the Fe-Ge films are ferromagnetic even above room temperature. A Hall sensitivity as large as 82 VAT was obtained in the Fe0.67 Ge0.33 film with a thickness of 4.1 nm. More importantly, it was found that the Hall sensitivity does not depend on the temperature in the temperature range of 50-300 K. In addition, the Hall resistance depends linearly on the magnetic field within the range of -2.5-2.5 kOe. This linear dependence, the larger sensitivity, and its temperature independence indicate that Fe-Ge films are potential material candidates for field sensors in a very broad temperature range.