Development of high permeability nanocrystalline permalloy by electrodeposition

Abstract

In this study, for developing microsensors for weak magnetic field, methods for developing high permeability nanocrystalline permalloy by electrodeposition and the relationship between the grain size and magnetic properties of the nanocrystalline permalloy are investigated. By dc plating with and without saccharin added and pulse plating with saccharin added, permalloy samples of grain sizes from 52 nm to 11 nm are obtained. The coercivity and magnetoimpedance (MI) ratio of the samples are tested against the grain size variation. Results show that the coercivity decreases rapidly and MI ratio increases greatly with grain size decrease from 52 nm to 11 nm.

Development of Ni80Fe20/Cu nanocrystalline composite wires by pulse-reverse electrodeposition

“…Hence, the addition of saccharin in the electrolyte solution reduces the average grain sizes of the deposits. For pulse electrodeposition (I A = 0), inhibiting species are absorbed onto the surface to inhibit grain growth during the off-time [5]. However, when |I A | > 0 and as I A increases, less saccharin molecules will be present at the wire surface during the electrodeposition process due to the alternating plating current to inhibit surface diffusion of adatoms.…”

“…The permeability increase could be due to a decrease in grain size below the exchange interaction length L ex , in which the effective anisotropy field decreases with the grain size. The exchange length L ex for permalloy was estimated to be 270 nm [5].…”

“…frequency, duty cycle, peak current density [2][3][4]). Pulse electrodeposition has been found to produce specimens of much lower grain size as compared to direct current electrodeposition [5]. Pulsereverse electrodeposition has been known to produce specimens of higher uniformity as compared to other electrodeposition methods [6].…”

Magnetic properties of high permeability NiFeMo/Cu composite wires

“…To develop such sensing elements, material studies on magnetic soft materials with high initial permeability and extremely low coercivity are important. Traditionally, Ni alloys such as permalloy Ni 79 Fe 21 [1][2][3][4] are known to possess extremely low coercivity and high magnetic permeability. It was also discovered that the addition of a trace amount of molybdenum to about the permalloy composition [5] would greatly enhance the magnetic properties.…”

Desenvolvimento de sensores magnéticos tipo fluxgate miniaturizados utilizando ligas ferromagnéticas eletrodepositadas.

“…Isto pode ser obtido pelo efeito Joule de uma corrente passada pelo fio em atmosfera inerte [59,57]. Exitem ainda outras técnicas de eletrodeposição, como pulsada, em que o tamanho do grão cristalino pode ser controlado [78] e deposição sob um campo longitudinal onde pode-se controlar o alinhamento dos grãos [79]. É possível também utilizar múltiplos fios a fim de melhorar a responsividade [76] e diminuir o ruído [80].…”