課題番号 ：S-18-MS-1013
利用形態 ：機器センター施設利用
利用課題名（日本語） ：Ni/Cu多層細線, NiMnGaナノ粒子の磁気的性質の解明
Program Title (English) ：Magnetic Properties of Ni/Cu multilayered nanowires and NiMnGa nanoparticles
利用者名（日本語） ：嶋　睦宏1)
Username (English) ：M. Shima1)
所属名（日本語） ：1) 岐阜大学工学部化学・生命工学科
Affiliation (English) ：1) Department of Chemistry and Biomolecular Science, Gifu University

1. Summary
“Spintronics” is a field of advanced technology that has been developed in recent years. Heusler alloys known as half metals are theoretically predicted to have 100% spin polarization which is one of the most important traits of magnetic materials in spintronics. Among them, Co-Fe based alloys such as Co2FeGa in the L21 ordered phase are particularly expected to have high spin polarization at room temperature because of their high Curie temperatures. Though nanostructured materials are in high demands for spintronic applications, the study of Co2FeGa alloys nanoparticles has not been clarified well. Hence the objectives of this study is to clarify the correlations between the structure and magnetic properties of Co-Fe and Co-Fe-Ga alloy nanoparticles. Co0.5Fe0.5-yGay ternary alloy nanoparticles in L21 ordered phase are synthesized by co-precipitation in the range of 0.20 ≤ y ≤ 0.27 when annealing temperature Ta is 973 K, and 0.17 ≤ y ≤ 0.24 when Ta is 1173 K though bulk doesn’t have it when Ta ≥ 1123 K. With increasing y, lattice parameter increases and crystallite diameter t is nearby constant. Degree of L21 order also decreases with increasing y, however degree of B2 order increases.

2. Experimental
First, Co(NO3)26H2O, Fe(NO3)39H2O and Ga(NO3)3nH2O were dissolved into water. Subsequently, Co-Fe-Ga and Co-Fe precursors were precipitated while NH3(aq) was added into the solution. The precipitates were air-dried at 343 K for more than 12 h and milled by a mortar and pestle to prepare powder samples. The powder samples were annealed at various temperatures (Ta = 873-1273 K) for 3 h in a mixture of N2 and H2 gases to obtain Co-Fe-Ga and Co-Fe alloy nanoparticles. The composition of the samples was examined by SEM-EDX, the structure was analyzed by XRD and the magnetic properties were measured by VSM and SQUID.

3. Results and Discussion
First, the structure and magnetic properties of CoxFe1-x binary alloy nanoparticles were examined. Their structure was found to depend not only on annealing temperature but also on their composition. XRD peaks for the bcc phase are observed when x ≦ 0.9, while those of the fcc phase are obtained when x ≧ 0.7, showing that a phase transition occurs in the range 0.7 < x < 0.9. Peaks for the B2 ordered phase are not detected though the lattice parameters are fairly close to that of the B2 phase. Their magnetization depends on both annealing temperature and their composition, which is shown to represent the Slater-Pauling curve. Co-Fe-Ga samples were synthesized at various composition ratio of Fe and Ga with fixed Co composition at 0.5 (Co0.5Fe0.5-yGay). The XRD spectra of the ternary alloy nanoparticles annealed at 973 K are shown in Fig. . The peaks corresponding to the Co2FeGa disordered phase are obtained from all the samples. Though the peak intensities of the L21 and B2 ordered phases are much smaller than that of the disordered phase, the peaks for the L21 phase are observed when 0.2 ≦ y ≦ 0.27. The degree of order decreases when y increases. All the samples annealed at 973 and 1173 K yield a ferromagnetic hysteresis loop at 300 K. The saturation magnetization decreases with increasing y (see Fig. 2). Saturation magnetization Ms of these samples are plotted in Fig. 3. The black dots show the samples annealed at 973 K and the red dots show the samples annealed at 1173 K. y = 0 shows the data of Co0.5Fe0.5. Saturation magnetization decreases linearly with increasing y. 4. Others N/A 5. Publication/Presentation (1) K. Yamada, S. Kondo, and M. Shima, The effects of Al/Fe ratio on the magnetic and fluorescence properties of (Yb,Gd)3(Sc,Al,Fe)5O12 garnet, Jpn. J. Appl. Phys. 57, 093001, 2018. (1) K. Yamada, Y. Kurokawa, K. Kogiso, H. Yuasa, and M. Shima, Observation of longitudinal spin seebeck voltage in YIG films chemically prepared by co-precipitation and spin coating, IEEE Trans. Magn. 55, 8463515, 2019. (3) 菊池真由，山田啓介，仲谷栄伸，嶋睦宏, 第79回応用物理学会秋季学術講演会，平成30年9月19日. (4) 林兼輔、山田啓介、嶋睦宏, 第79回応用物理学会秋季学術講演会，平成30年9月19日. (5) 小木曽一磨, 山田啓介, 塩田陽一, 森山貴広, 小野輝男, 嶋睦宏, 第79回応用物理学会秋季学術講演会，平成30年9月19日. 6．Patent N/A