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Hussain, Imad,Anwar, Mohammad Shafique,Khan, Saima Naz,Lee, Chan Gyu,Koo, Bon Heun Materials Research Society of Korea 2018 한국재료학회지 Vol.28 No.8
We report the structural, magnetic and magnetocaloric properties of $Sr_{1.8}Pr_{0.2}FeMo_{1-x}W_xO_6$($0.0{\leq}x{\leq}0.4$) samples prepared by the conventional solid state reaction method. The X-ray diffraction analysis confirms the formation of the tetragonal double perovskite structure with a I4/mmm space group in all the synthesized samples. The temperature dependent magnetization measurements reveal that all the samples go through a ferromagnetic to paramagnetic phase transition with an increasing temperature. The Arrott plot obtained for each synthesized sample demonstrates the second order nature of the magnetic phase transition. A magnetic entropy change is obtained from the magnetic isotherms. The values of maximum magnetic entropy change and relative cooling power at an applied field of 2.5 T are found to be $0.40Jkg^{-1}K^{-1}$ and $69Jkg^{-1}$ respectively for the $Sr_{1.8}Pr_{0.2}FeMoO_6$ sample. The tunability of magnetization and excellent magnetocaloric features at low applied magnetic field make these materials attractive for use in magnetic refrigeration technology.
Hussain, Imad,Anwar, M.S.,Khan, S.N.,Shahee, Aga,Ur Rehman, Zeeshan,Heun Koo, Bon Elsevier 2017 CERAMICS INTERNATIONAL Vol.43 No.13
<P><B>Abstract</B></P> <P>Fine-tuning the charge distribution in Ba<SUB>2</SUB>FeMoO<SUB>6</SUB> obtained via “isovalent” substitution at the A-site (i.e., Ba) is expected to bring about changes in the physical properties of the system that can be manipulated in magnetic refrigerants. With this motivation, the phase formation, crystal structure, microstructure, magnetic and magnetocaloric properties of the Ba<SUB>2−x</SUB>Sr<SUB>x</SUB>FeMoO<SUB>6</SUB> (0≤x≤0.4) samples fabricated by solid state reaction method have been investigated. The X-ray diffraction analysis confirmed the formation of cubic structure with <I>Fm</I>3<I>m</I> space group in all the fabricated samples. The magnetization measurements and Arrott analysis revealed a second order of ferromagnetic phase transition in all the samples. An increase in magnetization and Curie temperature (T<SUB>C</SUB>) was observed with the increase in Sr-content that was attributed to the increased orbital hybridization and exchange interaction between Fe and Mo ions. The magnitude of the maximum magnetic entropy change at the Curie temperature and the relative cooling power were observed to slightly decrease with the increased Sr doping. The excellent magnetocaloric features and convenient adjustment of Curie temperature make these materials useful for magnetic refrigeration in a wide range of temperature.</P>
Hussain, Imad,Anwar, M.S.,Kim, Eunji,Koo, Bon Heun,Lee, Chan Gyu Materials Research Society of Korea 2016 한국재료학회지 Vol.26 No.11
$La_{1-x}Ba_xMnO_3$ (x = 0.30, 0.35 and 0.40) samples have been prepared by solid-state reaction method. The X-ray diffraction (XRD) study showed that all the samples crystallized in a rhombohedral structure with an R-3c space group. Variation of the magnetization as a function of the temperature and applied magnetic field was carried out. All the samples revealed ferromagnetic to paramagnetic (FM-PM) phase transition at the Curie temperature $T_C{\sim}342K$. The magnetic entropy change was also studied through examination of the measured magnetic isotherms M(H, T) near $T_C$. The magnetocaloric effect was calculated in terms of the isothermal magnetic entropy change. The maximum entropy change reaches a value of 1.192 J/kgK under a magnetic field change of 2.5T for the $La_{0.6}Ba_{0.4}MnO_3$ composition. The relative cooling power (RCP) is 79.31 J/kg for the same applied magnetic field.
Hussain, Imad,Lee, Ji Eun,Jeon, So Eun,Cho, Hyun Ji,Huh, Seok-Hwan,Koo, Bon Heun,Lee, Chan Gyu Materials Research Society of Korea 2018 한국재료학회지 Vol.28 No.10
We report the structural, morphological and magnetic properties of the $Ni_{70}Mn_{30}$ alloy prepared by Planetary Ball Mill method. Keeping the milling time constant for 30 h, the effect of different ball milling speeds on the synthesis and magnetic properties of the samples was thoroughly investigated. A remarkable variation in the morphology and average particle size was observed with the increase in milling speed. For the samples ball milled at 200 and 300 rpm, the average particle size and hence magnetization were decreased due to the increased lattice strain, distortion and surface effects which became prominent due to the increase in the thickness of the outer magnetically dead layer. For the samples ball milled at 400, 500 and 600 rpm however, the average particle size and hence magnetization were increased. This increased magnetization was attributed to the reduced surface area to volume ratio that ultimately led to the enhanced ferromagnetic interactions. The maximum saturation magnetization (75 emu/g at 1 T applied field) observed for the sample ball milled at 600 rpm and the low value of coercivity makes this material useful as soft magnetic material.
Hussain, Imad,Khan, S.N.,Kim, Eun Ji,Jeon, So Eun,Koo, Bon Heun Elsevier 2018 Ceramics international Vol.44 No.3
<P><B>Abstract</B></P> <P>A systematic study focusing on the effect of Niobium (Nb) doping on the structural, magnetic and magnetocaloric properties of Ba<SUB>2</SUB>FeMoO<SUB>6</SUB> samples is presented here. The samples of interest Ba<SUB>2</SUB>FeMo<SUB>1−x</SUB>Nb<SUB>x</SUB>O<SUB>6</SUB> (0 ≤ x ≤ 0.4) were prepared using the solid state reaction method and were confirmed to possess a cubic structure with Fm-3m space group using the X-ray diffraction analysis and Rietveld refinement. A second order of ferromagnetic phase transition was recorded in both the pure as well as the Nb doped samples using the temperature dependent magnetization and Arrott plots analysis. The pristine Ba<SUB>2</SUB>FeMoO<SUB>6</SUB> (BFMO) sample indicated a spontaneous magnetization (34.6emu/g at 100K) with a relatively sharp magnetic transition at the Curie temperature (T<SUB>C</SUB>) of 315K as compared to the doped samples. A magnetic entropy change of 0.93 Jkg<SUP>−1</SUP>K<SUP>−1</SUP> at an applied magnetic field of 2.5T was measured for the pure BFMO sample. The doped BFMO samples with Mo partially substituted by Nb however, were observed to effectively modify the T<SUB>C</SUB> accompanied by a decrease in magnetization. The results investigated in this work suggest that the magnetic and magnetocaloric properties of the BFMO can be tailored by controlled Nb doping which is of significant importance in order to realize the numerous potential applications of the material in the magnetic refrigeration technology.</P>
Hussain, Imad,Khan, S.N.,Rao, Tentu Nageswara,Tsendenbal, Bulgan,Koo, Bon Heun Elsevier 2019 Solid state sciences Vol.94 No.-
<P><B>Abstract</B></P> <P>Double perovskite Sr<SUB>2</SUB>FeMo<SUB>0.9</SUB>B<SUB>0.1</SUB>O<SUB>6</SUB> materials doped with fixed amount of various transition metals (B = Mo, Nb, V, W) were synthesized using the solid state reaction method and investigated for their magnetic and magnetocaloric performance. X-ray diffraction profiles of the samples established tetragonal crystal structure with I4/mmm space group in these materials. A strong variation in the magnetization and Curie temperature values was observed in these samples as a result of transition-metal doping. The magnetization measurements and Arrott plots revealed a second order nature of magnetic phase transition in the investigated samples. The magnetocaloric effects in terms of the magnetic entropy change and relative cooling power (RCP) were calculated from the isothermal magnetization curves of the samples. The V-doped sample among the entire batch exhibited a maximum magnetic entropy change of 0.55 J/kg K with an RCP value of 60 J/kg at an applied magnetic field of 2.5 T. The tunability of magnetization, Curie temperature and magnetocaloric features in these materials at low applied field make them very attractive for use in solid state magnetic refrigeration technology.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Investigation of the structural, magnetic and magnetocaloric properties of different transition metals doped Sr<SUB>2</SUB>FeMoO<SUB>6</SUB>. </LI> <LI> Increased magnetization and magnetocaloric properties with transition metal doping. </LI> <LI> Tuning of the magnetization, Curie temperature and magnetocaloric properties with controlled transition metal doping. </LI> <LI> Second order of ferromagnetic phase transition with soft ferromagnetic properties. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Magnetization as a function of temperature in the Sr<SUB>2</SUB>FeMo<SUB>0.9</SUB>B<SUB>0.1</SUB>O<SUB>6</SUB> samples with B = (Mo, Nb, V, W).</P> <P>[DISPLAY OMISSION]</P>
Hussain, Imad,Anwar, M. S.,Khan, S. N.,Kim, Eunji,Koo, Bon Heun American Scientific Publishers 2017 Journal of Nanoscience and Nanotechnology Vol.17 No.11
<P>The effect of Iron (Fe) doping on the structural, magnetic and magnetocaloric properties of polycrystalline samples of Pr0.6Sr0.4MnO3 was investigated. Doped samples Pr0.6Sr0.4Mn1_xFexO3 with two different amounts of iron (x = 0.05, 0.1) as well as a pure undoped sample were prepared using the conventional solid state reaction method and were thoroughly investigated and compared. The X-rays diffraction analysis (XRD) established an orthorhombic structure with Pbnm space group in all samples. A second order nature of magnetic transition was confirmed using magnetization measurements and Arrott plots. A decrease in magnetization and Curie temperature was observed in the samples with higher amount of iron. A maximum value of magnetic entropy change 2.76 Jkg(-1)k(-1) at an applied magnetic field of 2.5 T and a relative cooling power (RCP) of 127 Jkg(-1) was observed in parent sample. The large magnetic entropy change, soft ferromagnetic properties and large RCP values make these compounds potential candidates for magnetic refrigeration.</P>
Tentu Nageswara Rao,Imad Hussain,Riyazuddin,Bon Heun Koo 한양대학교 세라믹연구소 2019 Journal of Ceramic Processing Research Vol.20 No.4
Graphene doped zinc oxide nanoparticles (G-ZnO) were prepared using modified hummer’s technique together with the ultrasonic method and characterized by field emission scanning electron microscopy (FESEM), X-ray powder diffraction (XRD), fourier-transform infrared spectroscopy (FTIR) and high-resolution transmission electron microscopy (HRTEM). Different samples of epoxy resin nanocomposites reinforced with G-ZnO nanoparticles were prepared and were marked as F1 (without adding nanoparticles), F2 (1% w/w G-ZnO), and F3 (2% w/w G-ZnO) in combination of ≈ 56:18:18:8w/w% with epoxy resin/hardener, ammonium polyphosphate, boric acid, and Chitosan. The peak heat release rate (PHRR) of the epoxy nanocomposites was observed to decrease dramatically with the increasing G-ZnO nanoparticles. However, the LOI values increased significantly with the increase in wt % of G-ZnO nanoparticles. From the UL-94V data, it was confirmed that the F2 and F3 samples passed the flame test and were rated as V-0. The results obtained in the present work clearly revealed that the synthesized samples can be used as efficient materials in fire-retardant coating technology.