Structure, Raman spectroscopy, and magnetic properties of new Al, Ga, and Mn-based high entropy oxides

Abstract

Recent advancements in high entropy oxides (HEOs) have sparked significant interest as a promising frontier in materials research, revolutionizing the landscape of material design and properties. They exhibit outstanding stability, intriguing functional properties, and unparalleled design flexibility enabled by the inclusion of multiple cations in these materials. In this study, we successfully stabilized several new high entropy spinel oxides with compositions (Ni0.2(Mg/Mn)0.2Co0.2Cu0.2Zn0.2)B2O4 (B = Al, Ga, Mn). The room temperature X-ray diffraction (RT-XRD), field emission scanning electron microscopy (FE-SEM), and energy dispersive spectroscopy (EDS) measurements highlight the crystal structure of the materials with excellent chemical homogeneity at the micro-scale. RT-XRD and Raman spectroscopy confirmed the formation of single-phase cubic spinel structures. However, the Mn-based sample exhibited tetragonal distortion. Magnetic measurements show remarkable variation in the magnetic properties: (Ni0.2Mg0.2Co0.2Cu0.2Zn0.2)Mn2O4 shows complex ferrimagnetic behavior, Al and Ga based diamond lattice (Ni0.2Mg0.2Co0.2Cu0.2Zn0.2)B2O4 (B = Al and Ga) materials revealed extremely high magnetic frustration and absence of magnetic ordering down to 1.8 K, indicative of exotic frustrated state. Magnetic transitions (spin-glass like) are observed in (Ni0.2Mn0.2Co0.2Cu0.2Zn0.2)B2O4 (B = Al and Ga) materials. Our study highlights the potential to finely tune the magnetic responses through compositional engineering, thus paving the way for the development of tailored magnetic materials for various applications.