Browsing by Author "Park, Jihoon"
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Item Electronic structures of MnB soft magnet(2016) Park, Jihoon; Hong, Yang Ki; Kim, Hyun Kyu; Lee, Woncheol; Yeo, Chang Dong (TTU); Kim, Seong Gon; Jung, Myung Hwa; Choi, Chul Jin; Mryasov, Oleg N.We have calculated the electronic structure of MnB using first-principles calculations based on the density functional theory within the local-spin-density approximation. The temperature dependence of saturation magnetization [Ms(T)] was calculated by mean field approximation. The calculated density of states (DOS) shows that the energy region near the Fermi energy (EF) is mostly attributed to the d bands of Mn. The saturation magnetizations (Ms) of MnB were calculated to be 964.5 emu/cm3 (1.21 T) at 0 K and 859.3 emu/cm3 (1.08 T) at 300 K. The calculated Ms at 300 K is in good agreement with experimental Ms of 851.5 emu/cm3.Item Magnetocrystalline anisotropy of interstitially and substitutionally Sn-doped MnBi for high temperature permanent magnet applications(2023) Choi, Minyeong; Hong, Yang Ki; Won, Hoyun; Yeo, Chang Dong (TTU); Choi, Byung Chul; Park, Jihoon; Lee, WoncheolFirst-principles calculations were performed to calculate the electronic structures of low temperature phase (LTP) MnBi (Mn50Bi50) and substitutionally and interstitially Sn-doped MnBi [Mn50Bi25Sn25, (Mn0.5Bi0.5)66.7Sn33.3]. Brillouin function predicts the temperature dependence of saturation magnetization M(T). Sn substitution for Bi in MnBi (Mn50Bi25Sn25) changes the magnetocrystalline anisotropy constant (Ku) from −0.202 MJ/m3 (the in-plane magnetization) for LTP MnBi to 1.711 MJ/m3 (the out-of-plane magnetization). In comparison, the Ku remains negative but slightly decreases to −0.043 MJ/m3 when Sn is interstitially doped in MnBi [(Mn0.5Bi0.5)66.7Sn33.3]. The Curie temperature (TC) decreases from 716 K for LTP Mn50Bi50 to 445 K for Mn50Bi25Sn25 and 285 K for (Mn0.5Bi0.5)66.7Sn33.3. Mn50Bi25Sn25 has a lower magnetic moment of 5.034 μB/f.u. but a higher saturation magnetization of 64.2 emu/g than (Mn0.5Bi0.5)66.7Sn33.3 with a magnetic moment of 6.609 μB/f.u. and a saturation magnetization of 48.2 emu/g because the weight and volume of the substitutionally Sn-doped MnBi are smaller than the interstitially Sn-doped MnBi. The low Curie temperature and magnetization for Sn-doped MnBi are attributed to the high concentration of Sn. Thus, future study needs to focus on low Sn-concentrated MnBi.