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Structural, Magnetic, and Electrical Properties of RE Doped Sr0.82RE0.18Fe12-xAlxO19(RE = Gd, Pr, Sm) Compound

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Advances in Materials Physics and Chemistry 2019年第9期9卷 175-198页

作者： Dom Lal Kunwar Dipesh Neupane jiba nath dahal Sanjay R.Mishra Department of Physics and Material Science The University of MemphisMemphisTNUSA Department of Physics Kent State UniversityKentOHUSA Department of Engineering Technology The University of MemphisMemphisTNUSA Department of Physics Truman State UniversityKirksvilleMOUSA

Among the family of ferrites, M-type hexaferrites has many industrial applications ranging from simple magnets to microwave devices. Improvement in magnetic and dielectric properties of ferrites is of continuous interest. In this present work details study is done to observe the effect of co-doping of rare-earth (RE3+: Pr3+, Sm3+, and Gd3+) and aluminum in Sr0.82RE0.18Fe12-xAlxO19 (x = 0.0, 0.5, 1.0, 1.5, 2.0). The adopted samples were synthesized via autocombustion technique. Detailed synthesis, structural, magnetic, and electrical measurements of samples were performed to understand structural-magnetic-electrical property relationship. The Al3+ substitution for Fe3+ brings in a significant enhancement in coercivity but reduces magnetization due to the magnetic dilution effect. Additional coercivity enhancement was possible with RE3+ doping without affecting the magnetization of samples. Among all RE3+ doped samples, Pr3+ doped samples showed the highest Curie temperature, (Tc ~ 465℃), while Gd3+ doped samples showed little variation in dielectric properties in GHz frequency range. This makes RE3+ doped samples as an ideal candidate for high-frequency microwave applications. Pr3+ with oblate charge distribution (negative Stevens constant) was observed to substitute well into the lattice consequently bringing in desired improvements in physical properties of Sr0.82RE0.18Fe12-xAlxO19 ferrite.

关键词： Sr-Ferrite Nanocomposite Magnetization Curie Temperature Coercivity Dielectric Constant

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Analysis of the Resolution of Crime Using Predictive Modeling

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Open Journal of Statistics 2020年第3期10卷 600-610页

作者： Keshab R. dahal jiba N. dahal Kenneth R. Goward Oluremi Abayami Department of Statistics Truman State University Kirksville MO USA Department of Physics Truman State University Kirksville MO USA Department of Mathematics SUNY Cortland Cortland NY USA Department of Mathematics Northwood University Midland MI USA

There has been evidence of crime in the US since colonization. In this article, we analyze the crime statistics of San Francisco and its resolution of crime recorded from January to September of the year 2018. We define resolution of crime as a target variable and study its relationship with other variables. We make several classification models to predict resolution of crime using several data mining techniques and suggest the best model for predicting resolution.

关键词： Machine Learning Classification Model Comparison Predictive Modeling Resolution of Crime

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Co-Doped Rare-Earth (La, Pr) and Co-Al Substituted M-Type Strontium Hexaferrite: Structural, Magnetic, and Mossbauer Spectroscopy Study

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Materials Sciences and Applications 2020年第7期11卷 474-493页

作者： Madhav L. Ghimire Dom L. Kunwar jiba N. dahal Dipesh Neupane Sunghyun Yoon Sanjay R. Mishra Department of Physics and Materials Science The University of Memphis Memphis TN USA Department of Physics Virginia Commonwealth University Richmond VA USA Department of Physics Kent State University Kent OH USA Department of Physics and Astronomy Truman State University Kirksville MO USA Department of Physics Gunsan National University Gunsan South Korea

The present study investigates the influence of La3+ and Pr3+ doping on the structural, magnetic properties, and hyperfine fields of Sr0.7RE0.3Fe12-2x CoxAlxO19, (RE: La3+ and Pr3+, x = 0.0 - 0.8) hexaferrite compounds prepared via auto-combustion technique. The XRD analysis shows a linear decrease in a and c lattice and unit cell volume contraction with the content x. The room temperature magnetic study shows that for the Pr3+ doped Sr0.7Pr0.3Fe12-2x CoxAlxO19 (Pr3+-SrM), the magnetization value monotonically decreases while for La3+ doped Sr0.7La0.3Fe12-2xCoxAlxO19 (La3+-SrM) magnetization value shows a noticeable increase in magnetization value with x. The coercivity of the Pr3+-SrM compound was observed to decrease while that of the La3+-SrM compound showed a marked 40% increase at x = 0.2 (~5829 Oe) in comparison to undoped SrFe12O19 (~3918 Oe). A difference in Curie temperature was also observed, with Tc ~ 525°C at x = 0.4 for Pr3+-SrM and Tc = 505°C for x = 0.4 for La3+-SrM compound. The observed differences in magnetic properties have been explained on the basis of the site occupancy of Co2+ and Al3+ in the presence of rare-earth ions. The presence of non-magnetic rare-earth ion, La3+, improved saturation magnetization, and coercivity and deemed suitable replacement for Sr2+. The hyperfine parameters namely quadrupole shift showed a decrease with the La3+ or Pr3+ doping independent of (Co2+-Al

关键词： Doped Hexaferrite M-Type Hexaferrite X-Ray Diffraction Mossbauer

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