1.Key Laboratory of Magnetism and Magnetic Materials, Ministry of Education, Lanzhou University, Lanzhou 730000, China 2.Key Laboratory of Special Function Materials and Structural Design, Ministry of Education, Lanzhou University, Lanzhou 730000, China
Abstract:In this paper, Ni88Cu12 thin films are prepared on Si substrates by radio-frequency magnetron co-sputtering. The effects of film thickness and heat treatment on domain structure and magnetic properties are studied. The Ni88Cu12 films with thickness less than 210 nm show weak in-plane anisotropy. After the vacuum magnetic field heat treatment, the crystal grains of all films grow, and the in-plane anisotropy extents of Ni88Cu12 films with thickness less than 210 nm become weaker. The films have different morphological characteristics at different heat treatment temperatures. The surface of the film is very dense before heat treatment. After heat treatment at 300 °C, it forms island shape due to the solid solution between the grains. Compared with the grains on the surface of the heat-treated film at 300 °C, the grains grow further after being heat-treated at 400 °C. Grown grains cover the gaps between the grains, which makes the film surface flat. The results of in-plane normalized hysteresis loop of the films show that the critical thickness of the stripe domains decreases after heat treatment. The stripe domain structure appears in the 210-nm-thick films without being heat-treated. For the film with the heat treatment, its remanence ratio Mr/Ms decreases, and the saturation field Hs increases, and thus leading the perpendicular anisotropy constant Kp to increase. Therefore, the thickness of the stripe domain in the film after being heat-treated decreases. Compared with the films after being heat-treated, the 105-nm-thick as-prepared Ni88Cu12 film has a maximum natural resonance frequency of 2.1 GHz, which is attributed to the uniaxial anisotropy of the as-prepared Ni88Cu12 film. The saturation magnetization of the 300 °C-treated 105-nm-thick film decreases to 3.01 × 105 A/m. However, the saturation magnetization decreases to 5.9 × 105 A/m after heat treatment at 400 °C. Moreover, the ferromagnetic resonance peak of the film narrows after being treated at 300 °C, and the resonance frequency decreases to 1.95 GHz. Keywords:stripe domain/ Ni88Cu12/ heat treatment
图 1 斜溅射制备磁性薄膜示意图(HA, 难轴方向)
图 2 未进行热处理的膜厚为(a) 105 nm, (b) 210 nm和(c) 262 nm的Ni88Cu12薄膜的MFM图像; (d)不同厚度Ni88Cu12薄膜的面内归一化磁滞回线; (e)薄膜的Mr/Ms随薄膜厚度的变化
图 3 (a)厚度为105 nm的Ni88Cu12薄膜热处理前后的XRD图谱; 厚度为105 nm的Ni88Cu12薄膜在(b)热处理前、(c) 300 oC热处理后和(d) 400 oC热处理后的SEM形貌图
图 4 (a)厚度为105 nm的Ni88Cu12薄膜在热处理前后的归一化磁滞回线; (b)厚度为105 nm的Ni88Cu12薄膜在热处理前、(c) 300 ℃热处理后和(d) 400 ℃热处理后的MFM图像
图 5 厚度为105 nm的Ni88Cu12薄膜热处理前后磁谱
