Contents lists available at ScienceDirect Journal of Magnetism and Magnetic Materials journal homepage: www.elsevier.com/locate/jmmm Research articles Study on magnetic and electrical properties of CoFeTaBO films with different oxygen content based on two-state model Cheng Chen a,c , Chengyue Xiong b , Changfeng Li a , Zhihao Wang a , Siqi Yin b , Xiufeng Huang a , Hong-Guang Piao a , Liqing Pan a , Xiaozhong Zhang b a Research Institute for Magnetoelectronics & Weak Magnetic-Field Detection, College of Science, China Three Gorges University, Yichang 443002, PR China b Key Laboratory of Advanced Materials (MOE) and Beijing National Center for Electron Microscopy, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, PR China c Department of Physics, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea ARTICLE INFO Keywords: Ferromagnetic films Amorphous materials Metallic oxides Magnetic properties Electrical properties ABSTRACT Amorphous magnetic CoFeTaBO granular films with different oxygen contents are fabricated by using magne- tron sputtering. The effect of oxygen contents on magnetic and electrical properties of the amorphous CoFeTaBO granular films are investigated, and a model for the coexistence of two states of oxygen-dependent metallic oxides in the CoFeTaBO film is proposed to explain magnetic and electrical characteristics in amorphous film system. It is expected that our proposed two-state model can provide a new perspective for understanding the physical properties of amorphous magnetic granular film materials. 1. Introduction Because of excellent mechanical properties [1–3], soft magnetic properties [4–6] and corrosion resistance [7,8], Iron-based amorphous alloy materials have become one of the hot topics in the field of func- tional materials. Recently, it has been found that some iron-based amorphous alloy material not only have conventional amorphous alloy properties but also show semiconductor-like electrical properties, which has the dependence of resistivity on temperature and the ex- istence of optical band gap, such as FeCu [9], FeCoTiHfB [10], FeSi [11] and CoFeTaB [12,13] etc. For the amorphous CoFeTaB alloys, it has received a lot of attention because its electrical properties can be ad- justed by changing the preparation conditions. For example, it can be formed an amorphous CoFeTaBO film with a semiconductor-like elec- trical property by introducing oxygen into the CoFeTaB alloy, while preserving the ferromagnetic properties of the alloy film [12–14]. The amorphous CoFeTaBO film presents a series of excellent features, such as high Curie temperature up to 600 K, optical energy band gap of ~2.5 eV, great light transmission (optically transparent) characteristic, etc. Due to the natural combination of magnetic, electrical, and optical properties in the amorphous CoFeTaBO film, it can simultaneously utilize the spin and charge of electron degrees which is beneficial to realize spintronics application. To prepare a high quality amorphous CoFeTaBO film, the effect of oxygen content on electrical and magnetic properties of the film were investigated from the points of chemical state of elements [15] and the percolation effect of oxygen [16]. In- terestingly, two states of amorphous metal oxides with high/low oxygen content are clearly observed in the CoFeTaBO film by high- angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and energy dispersive spectroscopy (EDS) mapping [13]. It can be inferred that the change of the proportion of the two components will affect physical properties of the amorphous CoFeTaBO alloy system. However, the effect of the microstructure change induced by oxygen introducing on various physical properties of the amorphous CoFeTaBO alloy system has not systematically discussed in many stu- dies. In this work, amorphous magnetic CoFeTaBO granular films with different oxygen contents are fabricated by using magnetron sputtering. The effect of oxygen contents on magnetic and electrical properties of the amorphous CoFeTaBO films are investigated. According to the ex- perimental result in the Ref. 13, a model for the coexistence of two states of oxygen-dependent metallic oxides in the CoFeTaBO film is proposed, expects which will explain magnetic and electrical char- acteristics in complex amorphous film systems. 2. Experiments Based on the Co 23.1 Fe 50.5 Ta 11.1 B 6.7 O 8.6 alloy target with a diameter of 60 mm, by using DC Magnetron Sputtering System (SKY Technology Development Co., JGP-560B), a series of amorphous CoFeTaBO films https://doi.org/10.1016/j.jmmm.2020.167285 Received 22 May 2020; Received in revised form 17 July 2020; Accepted 31 July 2020 E-mail addresses: hgpiao@ctgu.edu.cn (H.-G. Piao), lpan@ctgu.edu.cn (L. Pan). Journal of Magnetism and Magnetic Materials 515 (2020) 167285 Available online 03 August 2020 0304-8853/ © 2020 Elsevier B.V. All rights reserved. T