Magnetic properties and thermal stability of Co/HfN multilayer films for high-frequency application

Abstract

Sputtered metal–nonmetal granular films tend to exhibit growth-induced perpendicular magnetic anisotropy. In this work, Co/HfN multilayers were synthesized to suppress the development of columnar clusters along the deposition direction. The results reveal that a HfN interlayer thickness of less than 0.4 nm is insufficient to separate the columnar clusters; however, increasing the interlayer thickness to 0.8 nm with increasing the sputtering duration successfully led to typical in-plane magnetic anisotropy with a coercivity as low as 3 Oe. The Co(4 nm)/HfN(1.5 nm) multilayers exhibited high permeability of approximately 260 up to 1.6 GHz. The resonance frequency increased from 1.8 to 2.3 GHz with increasing annealing temperature, which is attributed to the increased magnetic anisotropy. Our results suggest that the multilayers still show high-frequency performance even after annealing at 450 °C, which would be a big advantage for complementary metal–oxide–semiconductor (CMOS) fabrication technology.

Rotatable magnetic anisotropy in Fe78Si9B13 thin films displaying stripe domains

“…Stripe domains in thin films have been observed since many decades in Ni-and Co-based systems [1][2][3][4][5], and later in a variety of thin films, including amorphous or nanocrystalline alloys [6][7][8][9][10][11], highly magnetostrictive alloys [12,13], and multilayers [14,15], and even in amorphous ribbons and bulk systems [16][17][18]. Their relatively weak perpendicular anisotropy is comparable to the shape anisotropy, and results in stripe domains whose magnetisation is tilted off the sample plane, therefore having both an in-plane and an out-of-plane component [11,19], with the possible presence of closure domains [20].…”

“…Any in-plane direction being equivalent, the reason why a threshold value for the applied magnetic field must be overcome to induce the stripes rotation along its direction is still not clear, in spite of detailed investigations of the static and dynamic magnetisation processes in this kind of samples [6,12,13,[22][23][24]. Understanding this phenomenon is still an open question that needs to be addressed in order to be able to transfer magnetic thin films having a controlled weak perpendicular anisotropy [25][26][27] into applications, including high-frequency [15,28] or biomedicine [29,30].…”

Room TemperatureMagnetoresistance Property of Co-TiO2 NanocompositeFilm Prepared by StrongMagneticTarget Co-sputtering

“…Key words: nanocomposite film; strong magnetic target co-sputtering; room temperature tunneling magnetoresistance; Co-TiO 2 近年来人们在隧道结、多层膜、颗粒膜等复合 材料中发现了电子自旋耦合作用, 并由此开发了一 系列具有良好应用前景的自旋电子器件, 其中包括 磁性传感器 [1] 、自旋纳米振荡器 [2] 和自旋逻辑器 [3] 等。随着人们对材料中电子运输机制的深入研究, 电子自旋器件也逐渐向着集成化、微型化的方向发 展 [4][5] 。其中, 纳米复合薄膜与传统的隧道结相比, 具有针孔效应少、 不易发生击穿、 易制备的特点, 因 此近年来得到了快速的发展 [6][7] 。但现阶段纳米复合 薄膜主要由氟化物或氮化物组成 [8][9][10] , 生物相容性 较差, 难以应用于生物、 医学等领域, 极大限制了纳 米复合薄膜的发展。为获得具有磁电阻效应和良好 生物相容性的纳米复合薄膜, 本研究采用磁控溅射 法将 Co 金属和 TiO 2 陶瓷进行复合。 金属 Co 与 Fe、 Ni 等磁性金属相比, 不易发生氧化, 在小颗粒尺寸 下可表现出较强磁性。而 TiO 2 具有良好的生物相容 性, 在光催化 [11] 、生物医学 [12][13] 和防腐 [14] 等领域得 到了广泛应用。根据近年来的报道, 在纳米复合薄 膜的制备过程中, 由于磁性金属和氧化物处在同一 溅射腔体内, Co 容易发生部分氧化 [15][16] [18] , 使用非强磁靶溅 [19] , 这表明薄膜中 Ti 元素主要以 二氧化钛的形式存在。图 3(b)为 Co 含量为 51.3at% 时, 薄膜 Co 元素的 XPS 图谱。 其中 796.0 和 780.1 eV 对应 Co 2+ 的 Co2p1/2 和 Co2p3/2 [20] , 而 792.3 和 777.3 eV 两个电子峰位分别对应金属 Co 的 Co2p1/2 和 Co2p3/2 [21] 。通过面积对比发现, 薄膜中大部分 Co 前的研究结果相比 [15][16]…”