VP9-07 Fe-Pt films prepared from plating baths containing glycine as a complexing agent
Creators: Yuito Yamaguchi
Takeshi Yanai
Naoki Yanai
Daiki Fukushima
Akiho Hamakawa
Akihiro Yamashita
Masaki Nakano
Hirotoshi Fukunaga
Publisher: name: IEEE
Year: 2025

Pt-based magnets are expected to be used in medical applications due to high crystalline magnetic anisotropy and excellent corrosion resistance. We have already reported electroplating Fe-Pt and Co-Pt films using plating baths with citric acid (pH = 2) [1,2]. Recently, we investigated the effect of Cl ions in the plating baths on the hard magnetic properties of the Fe-Pt films and reported that the Cl ions decrease the coercivity [3]. In the present study, we focused on glycine instead of citric acid as a complexing agent, to investigate the effect of the complex agent on the reduction of coercivity by the Cl ions. Firstly, we developed an electroplating process of Fe-Pt films using glycine-based baths and then investigated the effect of Cl ions on the coercivity. We electroplated Fe-Pt films on Cu substrates. The plating bath consisted of FeSO4･7H2O (2 g/L), Pt(NO2)2(NH3)2 (10 g/L), NH4NH2SO3 (30 g/L), and glycine. The plating conditions were (j = 1 A/mm2, t = 10 min, Tbath = 70°C) ,and pH = approximately 2.0. The plated Fe-Pt films were annealed at 700°C to transform the fcc structure to the fct one. Figure 1 shows the Fe composition and the coercivity of the annealed Fe-Pt films as a function of the amount of glycine in the plating bath. As shown in Fig.1, the Fe composition slightly increased with the increase in glycine. The coercivity showed almost the same value in the glycine amount from 10 to 40 g/L. In our experimental conditions, a high coercivity of 1,000 kA/m was obtained at 20 g/L, and this value was the same as that for the citric acid-based bath, as shown in the inset of Fig.1. Figure 2 shows the coercivity of the annealed Fe-Pt films as a function of the amount of FeCl2 in the plating bath. We added Cl ions to the plating bath by partially replacing FeSO4 with FeCl2. As shown in Fig.2, the coercivity decreased with increasing the FeCl2, indicating that a large amount of Cl ions in the plating baths is unsuitable for obtaining high coercivity. From Fig.2 and our previous studies for the citric-acid-based baths [3], we found that complex agents are not a factor in the reduction of coercivity by existing Cl ions in the baths.References: [1]T. Yanai, K. Furutani, T. Ohgai, M. Nakano, K. Suzuki, H. Fukunaga, “Fe-Pt thick-film magnets prepared by electroplating method”, Journal of Applied Physics. Vol.117, (2015) #17A744. [2]T. Yanai, R. Hamamura, J. Honda, A. Tomita, H. Yamada, N. Fujita, K. Takashima, M. Nakano, H. Fukunaga, "Electroplated Co-Pt thick-film-magnets prepared in citric-acid-based plating baths", IEEE Transactions on Magnetics, Vol.53 (2017) #2101803. [3]T. Yanai, D. Fukushima, R. Narabayashi, N. Ogushi, Y. Yamaguchi, A. Yamashita, M. Nakano, and H. Fukunaga, “Reduction effect of coercivity of electroplated Fe-Pt film magnets by chloride ion in plating baths”, AIP Advances, Vol. 14, (2024) #015032.
Pt-based magnets are expected to be used in medical applications due to high crystalline magnetic anisotropy and excellent corrosion resistance. We have already reported electroplating Fe-Pt and Co-Pt films using plating baths with citric acid (pH = 2) [1,2]. Recently, we investigated the effect of Cl ions in the plating baths on the hard magnetic properties of the Fe-Pt films and reported that the Cl ions decrease the coercivity [3]. In the present study, we focused on glycine instead of citric acid as a complexing agent, to investigate the effect of the complex agent on the reduction of coercivity by the Cl ions. Firstly, we developed an electroplating process of Fe-Pt films using glycine-based baths and then investigated the effect of Cl ions on the coercivity. We electroplated Fe-Pt films on Cu substrates. The plating bath consisted of FeSO4･7H2O (2 g/L), Pt(NO2)2(NH3)2 (10 g/L), NH4NH2SO3 (30 g/L), and glycine. The plating conditions were (j = 1 A/mm2, t = 10 min, Tbath = 70°C) ,and pH = approximately 2.0. The plated Fe-Pt films were annealed at 700°C to transform the fcc structure to the fct one. Figure 1 shows the Fe composition and the coercivity of the annealed Fe-Pt films as a function of the amount of glycine in the plating bath. As shown in Fig.1, the Fe composition slightly increased with the increase in glycine. The coercivity showed almost the same value in the glycine amount from 10 to 40 g/L. In our experimental conditions, a high coercivity of 1,000 kA/m was obtained at 20 g/L, and this value was the same as that for the citric acid-based bath, as shown in the inset of Fig.1. Figure 2 shows the coercivity of the annealed Fe-Pt films as a function of the amount of FeCl2 in the plating bath. We added Cl ions to the plating bath by partially replacing FeSO4 with FeCl2. As shown in Fig.2, the coercivity decreased with increasing the FeCl2, indicating that a large amount of Cl ions in the plating baths is unsuitable for obtaining high coercivity. From Fig.2 and our previous studies for the citric-acid-based baths [3], we found that complex agents are not a factor in the reduction of coercivity by existing Cl ions in the baths.References: [1]T. Yanai, K. Furutani, T. Ohgai, M. Nakano, K. Suzuki, H. Fukunaga, “Fe-Pt thick-film magnets prepared by electroplating method”, Journal of Applied Physics. Vol.117, (2015) #17A744. [2]T. Yanai, R. Hamamura, J. Honda, A. Tomita, H. Yamada, N. Fujita, K. Takashima, M. Nakano, H. Fukunaga, "Electroplated Co-Pt thick-film-magnets prepared in citric-acid-based plating baths", IEEE Transactions on Magnetics, Vol.53 (2017) #2101803. [3]T. Yanai, D. Fukushima, R. Narabayashi, N. Ogushi, Y. Yamaguchi, A. Yamashita, M. Nakano, and H. Fukunaga, “Reduction effect of coercivity of electroplated Fe-Pt film magnets by chloride ion in plating baths”, AIP Advances, Vol. 14, (2024) #015032.