Study On Magnetostrictive TbDyFe-FeNi Multilayers And Properties Of The Structure Of TbDyFe-FeNi Multilayers/Optic-Fiber

The magnetostriction in TbDyFe/FeNi multilayers prepared by DC magnetron sputtering is studied in this paper.The purpose is to find a new way to improve the magnetostriction of TbDyFe films.At the same time, the fibre-optic magnetic sensor system by means of TbDyFe/FeNi multilayer coating on the fiber is also demonstrated and to detect weak magnetic fields.Through the analyses to the structure,atomic content and surface morphology of the FeNi films, TbDyFe films and TbDyFe/FeNi multilayers deposited on Si substrates by X-ray diffraction,energy spectrum and scanning electron microscope, respectively,the results are as foUows.TheFeNi films are crystal while the TbDyFe films are amorphous.The microstructure of multilayers is made up of FeNi crystal and TbDyFe amorphous.The investigation on the magnetic properties shows that the easy axil of TbDyFe films is vertical to the surface,while FeNi monolays' and TbDyFe/FeNi multilayers' are parallel to the surface.The coercive force of the films is deduced largely the soft magnetic properties are boosted as a result of the addition of the soft magnetic FeNi films.The magnetostrictin of the multilayers is superior to the TbDyFe films and increases with the decrease of thickness of FeNi films. The magnetostriction of multilayers prepared under the adscititious magnetic field and annealing can be improved.The magnetic-mechanical-optical transfer relations in the optical fibre coated with TbDyFe/FeNi multilayers and the influences on it are demonstrated when it is exposed to applied filed parrel to the axial direction.The control model of the structure of TbDyFe/FeNi mutileyers/optic-fibre is also constructed.The results show that the phase delay of light propagating in the fiber is relative to the thickness of the film,and the conclusions of the two models are corresponded.The analysis of the composite structure of TbDyFe/FeNi multilayes/optic-fibre using the ANSYS soft ware hs been studied,and the finite element analysis program that can be use to search magnetostriction in the fils is provided.The results of it indicate that the thickness of multilayers has direct influence on the coupling relations,and the phase delay in the fibre increase with the increasing thickness of films. At the same time ,the magnitude of phase induced by defferent magnetic fields is calculated.A set of TbDyFe film/optical fibre sensor is demonstrated and tested using a Mach-Zehnder interferometer.It is revealed that the sensor exhibits the largest responses against applied AC magnetic fields at the frequency of about 4700Hz.There is a good linearity between the output signal and the AC magnetic field,the same to DC magetic fields.Minimum detectable fields of 2.34 × 10'4A/m is demonstrated over a range 0kA/m to 48 kA/m for the DC biasmagnetic field.The result is consistent with the value of ANSYS simulation.The experimentations also confirm that the sensitivity of detecting system can be improved by increasing films thickness,but it leads to disorderly and unsystematic relations between responsivity and frequency of Ac modulated magnetic fields.