VP19-09 Improvement in magnetic properties of soft magnetic films prepared from gel electrolyte
Creators: Kota Shiraki
Yusuke Matsumoto
Mayuri Tashiro
Takeshi Yanai
Akihiro Yamashita
Masaki Nakano
Hirotoshi Fukunaga
Publisher: name: IEEE
Year: 2025

Recently, we reported soft magnetic Ni films prepared from gel electrolytes and showed the potential of the gel-plating process [1]. In our previous study, we confirmed that the saturation magnetization, Ms, of the Ni films was smaller than that of bulk Ni, indicating that we need to improve the soft magnetic properties for gel-plating. In the present study, we, therefore, focused on the improvement in the current efficiency (C.E.) of the plating process, which is the ratio of the electroplated film's weight to the theoretical one obtained by Faraday's law, and investigated the effects of the current density, j, during the electroplating on the C.E. and Ms of Ni and Co films. The films were electroplated using a DC power supply. Metal (Ni or Fe) and Cu plates were used as an anode and a substrate, respectively. The gel electrolyte was filled between the electrodes. In our previous study, we employed j = 15 – 45 mA/mm2, and the results suggested that low current density is effective in obtaining a high deposition rate. In the present study, j was changed from 5 to 60 mA/cm2. Figure 1 shows the current efficiency of the plating processes as a function of the current densities As shown in Fig.1, since the decrease in the current density improves the C.E., we confirmed that increase in the deposition rate in our previous study [1] was attributed to the increase in the C.E. Figure 2 shows the hysteresis loops of the Co films. As shown in Fig. 2, the improvement in the C.E. increased the Ms. When the C.E. is low, the decomposition of H2O occurs on the cathode surface, generating H2 gases and (OH)- ions. Since it is considered that the (OH)- ions easily combine the metal ions M2+ (Ni2+ and Co2+), we considered that low Ms is affected by the oxidation of the Ni and Co. In other words, a gel-plating process with high C.E. is preferable to obtain good soft magnetic properties, and we found that the low current density is one of effective conditions in obtaining high C.E. and high Ms.References: [1] T. Yanai et al., AIP advances, Vol. 14, #025331 (2024).
Recently, we reported soft magnetic Ni films prepared from gel electrolytes and showed the potential of the gel-plating process [1]. In our previous study, we confirmed that the saturation magnetization, Ms, of the Ni films was smaller than that of bulk Ni, indicating that we need to improve the soft magnetic properties for gel-plating. In the present study, we, therefore, focused on the improvement in the current efficiency (C.E.) of the plating process, which is the ratio of the electroplated film's weight to the theoretical one obtained by Faraday's law, and investigated the effects of the current density, j, during the electroplating on the C.E. and Ms of Ni and Co films. The films were electroplated using a DC power supply. Metal (Ni or Fe) and Cu plates were used as an anode and a substrate, respectively. The gel electrolyte was filled between the electrodes. In our previous study, we employed j = 15 – 45 mA/mm2, and the results suggested that low current density is effective in obtaining a high deposition rate. In the present study, j was changed from 5 to 60 mA/cm2. Figure 1 shows the current efficiency of the plating processes as a function of the current densities As shown in Fig.1, since the decrease in the current density improves the C.E., we confirmed that increase in the deposition rate in our previous study [1] was attributed to the increase in the C.E. Figure 2 shows the hysteresis loops of the Co films. As shown in Fig. 2, the improvement in the C.E. increased the Ms. When the C.E. is low, the decomposition of H2O occurs on the cathode surface, generating H2 gases and (OH)- ions. Since it is considered that the (OH)- ions easily combine the metal ions M2+ (Ni2+ and Co2+), we considered that low Ms is affected by the oxidation of the Ni and Co. In other words, a gel-plating process with high C.E. is preferable to obtain good soft magnetic properties, and we found that the low current density is one of effective conditions in obtaining high C.E. and high Ms.References: [1] T. Yanai et al., AIP advances, Vol. 14, #025331 (2024).