Magnetic performance of orthorhombic Mn₃₅Ge₃₅Te₃₀ nanocrystals

Nanocrystalline antiferromagnetic Mn₃₅Ge₃₅Te₃₀ diluted magnetic semiconductors powder syntheses by the conventional direct reaction of pure metals. Nanocrystalline nature of the prepared sample confirmed using various techniques, where x-Ray diffraction (XRD) and atomic force microscope (AFM) measurements shows ~96 nm particle size, while transmission electron microscope (TEM) shows 92 nm particle size. XRD analysis show orthorhombic symmetry with lattice parameters a=7.386611±(0.0066) Å, b=8.962502±(0.0090) Å and c=7.027349±(0.0040) Å. Electron Spin resonance (ESR) show a broad asymmetric line whereas the remnant Mn²⁺ six-hyperfine lines are broadened within |+1/2>→|−1/2> line according to high anisotropy; calculated Landé g-factor is 2.047. Vibrating sample magnetometer (VSM) analysis, field-moment characteristics revealed a hysteresis loop with small coercive field indicating that Mn₃₅Ge₃₅Te₃₀ is a soft magnetic material. Moreover, hysteresis measurements at different temperatures show increasing magnetization with increasing temperature up to 150 K followed by decreased with increasing temperature up to 300 K. This behavior indicated to the antiferromagnetic nature of the prepared nanocrystalline materials. Magnetic moment – temperature measurements show Néel temperature T_N=172.6 K. Magnetic force microscope revealed magnetic domains as a result of interaction between magnetic dipole moments of magnetic cantilever and pressed powder. - Highlights: • Nanocrystalline diluted magnetic semiconductors of new Mn-Ge-Te orthorhombic phase. • Soft magnetic materials for a magnetic core of many devices. • Mixture of ferromagnetic and antiferromagnetic. • Asymmetry in hysteresis loop explained by the exchange bias of domain spins.