## 1 Introduction  
Fe-based amorphous soft magnetic composites were developed to prevent the malfunction of electronic devices due to electromagnetic interference in automobiles, ships and airplanes, as well as to shield a facility from electromagnetic pulse (EMP) activity. As the development of automatic-driving automobiles accelerates, and electric vehicles are being equipped with high-power motors, the density of electronics in automobiles has been increasing rapidly [1; 2; 3]. Electromagnetic waves emitted from the electrical signal cables in the car may cause interference, such as causing engines or electrical motors to accelerate without cause, and lead to an accident [4; 5; 6; 7]. In 1962, the U.S. Navy's [PERSON] aircraft carrier was on the brink of sinking from a huge fire as a result of malfunction in a missile due to electromagnetic interference [8]. Electronic and information communication devices, including computers and mobile phones, are small and typically transportable. Accordingly, electronic components have become more highly integrated, and the signal processing speed has accelerated as well. One of the most important factors that affects the reliability of these electronics and components is electromagnetic interference (EMI) [9; 10; 11; 12]. Interference caused by electromagnetic noise can cause malfunctions of the electronic equipment, as well as potential health problems (e.g., disease) by increasing the temperature of cells in a human body [13; 14; 15; 16]. Therefore, many countries have identified electromagnetic waves as carcinogens and are strengthening their regulations [17; 18; 19; 20; 21]. Meanwhile, electromagnetic compatibility (EMC) protects the inside of electronic devices from electromagnetic noise generated in external environments [22]. With the rapid development of electronic devices, the demand for these EMI/EMC-related materialsand components is growing, and electromagnetic wave shielding technologies have been developed as well [23; 24; 25; 26; 27; 28; 29]. Materials that prevent or reduce electromagnetic noise have been widely used in electronic devices and have recently been expanded to many new electronics, such as televisions, personal computers, smart mobile devices and phones, etc. [30]. Conventionally, the main module of the device was shielded with a thin film, such as copper, a conductive material, for protection against electromagnetic waves [31]. However, high shielding efficiency using only conductive materials for electromagnetic waves has limited application for the waves generated by magnetic fields. Therefore, conventional shielding materials were replaced with soft magnetic materials capable of shielding both the magnetic and electric fields' excellent permeability [32; 33; 34]. Table 1 shows the shielding effects of a representative soft magnetic material as compared to the conductive materials. Magnetic field shielding is more important than electric field shielding due to the frequency band of electromagnetic waves emitted from electronic devices being relatively low in the kHz range. However, electromagnetic wave shielding could be effective with only a conductive material, as the frequency increases beyond the MHz region. It is essential to use an electrical conductor with soft magnetic characteristics for the purpose of reducing the electromagnetic wave noise generated inside electronic devices and protecting them from external EMP attacks [35; 36; 37; 38]. Therefore, an amorphous soft magnetic material with high permeability and excellent electrical conductivity in the kHz frequency range was adopted as an electromagnetic wave-shielding material in this study. Table 2 shows soft magnetic properties of the magnetic specimen with high permeability and low coercivity. The objective of this study was to measure electromagnetic wave-shielding efficiency under various conditions using an amorphous soft magnetic sheet, which was a precursor (base material) for the amorphous soft magnetic fibers, and to identify the optimal composite material production.