Ligas magnéticas NiFe e NiFeCo eletrodepositadas, voltadas para aplicações em micro-sensores magnéticos tipo fluxgate planar / Electrodeposited NiFe and NiFeCo films for planar fluxgate sensors




This work presents the results about the fabrication and characterization of thin films of NiFe and NiFeCo alloys. The attempts to construct the planar fluxgate are also presented. Galvanostatic electrodeposition using an electrolytic solution containing Ni and Fe was used: NiSO4 (0,7 mol/l); NiCl2 (0,02 mol/l); FeSO4 (0,03 mol/l); H3BO3 (0,4 mol/l) and C7H5O3NS.2H2O (0,016 mol/l). The auxiliary electrode was made on Ni for the NiFe films, while another one made on Co was used for the NiFeCo films. Films were deposited on copper substrates using current densities form 4 up to 28 mA/cm2, and total deposition time of 40 and 60 minutes. Structural characterization was performed using Scanning Electron Microscopy (surface and cross-section); Energy Dispersive Spectroscopy, and Xray Diffraction. Magnetic characterization was performed using two methods: the Vibrating Sample Magnetometry and magnetometry using a SQUID (Superconducting Quantum Interference Devices) sensor. NiFe films grow with crystalline planes oriented along the (110) e (200) directions; the amount of each material reach constant values for current densities above 15 mA/cm2 (even though there is always more Ni). The point of minimum magnetic coercivity (58,4 A/m) also occurs for this current density, where films 1 ?m-thick are obtained for a total deposition time of 40 minutes. An asymmetry is observed for magnetic fields applied parallel and perpendicular to the surface of the films. NiFeCo films grow with crystalline planes oriented along the (111) and (200) directions; the amount of Ni remains constant (about 70%) for the whole current density range. The amount of Fe decreases with increasing current density, while the amout of Co shows the opposite behavior. They have equal values for current densities of about 15mA/cm2, where the minimum coercivity of 81A/m is achieved. For higher current densities the coercivity remains constant. For the current density of 15mA/cm2, 6 ?m-thick films are obtained for a total deposition time of 40 minutes. The magnetic asymmetry is smaller than for the case of the NiFe films. According to the obtained data, we believe that NiFeCo is a better candidate for the fabrication of planar magnetic fluxgate sensors. Initial tests for the fabrication of a prototype are also presented.


electrodeposition eletrodeposição magnetic sensor nife coercividade magnética planar fluxgate nife ligas magnéticas fluxgate planar nifeco magnetic coercivity nifeco micro-sensores magnéticos

Documentos Relacionados