## 4 Analytical Discussion
### Keywords Assessment  
The acquisition of keywords will aid in the development of new study topics and the evaluation of existing research. The co-occurrence of author keywords for the YIG field was determined. The keywords based on text data were described by the authors in the papers. The results are retrieved using the Scopus database, while the co-occurrence map was generated using VOS viewer software, as shown in Figure 6. This mapping method employing VOS viewer software is more advanced than the data counting method as it is more complex and allows for a greater interpretation [42]. VOS viewer is beneficial for visualizing big bibliometric maps in an easily interpretable approach [139]. According to VOS viewer, a total of 112 keywords were associated with the 799 publications of total articles. In the keyword co-occurrence map, the keywords are represented by colored nodes. The item's color nodes are determined by the cluster from which it was obtained. Moreover, the map depicts the various items and linkages that correspond to a variety of keywords, as well as the connection line. The stronger connection line signifies the large frequency of the item cluster. The size of nodes is proportional to the frequency with which the keywords occur, and the lines between nodes show their co-occurrence relationship. In the analysis based on VOS viewer, Figure 6 depicts six clusters on the map. For example, cluster one contains eleven different items including an anomalous Hall effect, interface, inverse spin-Hall effect, magnetic anisotropy, magnetic insulator, spin-current, spin-Hall effect, spin-Hall magnetoresistance, spin pumping, spin-Seebeck effect, and spintronics. Cluster two contains nine items, including the Faraday effect, Faraday rotation, garnets, magneto-optical properties, magneto-optics, perpendicular magnetic anisotropy, pulsed laser deposition, and thin films. The nine items included in Cluster 3 are ferrites, magnetic materials, magnetic properties, magnetism, magnons, microstructure, optical properties, sol-gel, and thin film. The seven items included in Cluster 4 are ferromagnetic resonance, gilbert damping, magnetization dynamic, magnonics, microwave magnetics, spin waves, and yttrium iron garnet. Curie temperature, ferromagnetic resonance, garnet, linewidth, magnetic property, magnetization, and yttrium iron garnet are included in Cluster 5 (contains 7 items). Cluster 6 comprises the final four items: magnetic damping, nanoparticles, saturation magnetization, and sol-gel. Figure 6: Co-occurrence of author keywords (number of occurrences 112 keywords). According to Figure 6 which was analyzed from VOS viewer, the six clusters of keywords represent the groups of works that are closely related:  
* Cluster 1: Recent spintronic phenomena such as the spin-Seebeck effect (SSE) and the spin-pumping effect have drawn substantial interest in magnetic garnets [16; 18; 35; 84]. The most frequent approach to detect SSE spin currents is to measure the charge current caused by the inverse spin-Hall effect (ISHE) in a nonmagnetic metallic (NM) layer in interface with the magnetic material [84]. Furthermore, a study topic has emerged that employs YIG/platinum structures for spintronics [14; 20]. Spintronics uses spin-polarized charge carriers for production, manipulation, and identification [20]. * Cluster 2: Magneto-optical devices require thin films with superior magnetic and structural properties [2]. The pulsed laser deposition (PLD) technique has been reported to provide superior control of layer thickness, surface roughness, stoichiometry, and magnetic characteristics for YIG thin film [2; 124]. YIG is very transparent at near-infrared wavelength regions [86], but its magneto-optical performance is quite weak. For magneto-optical devices, the Y in YIG thin film is partially replaced with rare earth garnet elements such as bismuth, cerium, or other rare earth, which can boost the Faraday rotation by an order of magnitude [11; 86; 124].