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Ferromagnetic Order in Rapidly Cooled Nd-Fe-Co-Al Alloy Ribbons
Phan, T. L.,Zhang, Y. D.,Dan, N. H.,Thang, D. D.,Thanh, T. D.,Zhang, P.,Yu, S. C. IEEE 2013 IEEE transactions on magnetics Vol.49 No.7
<P>We have studied the magnetic properties of Nd<SUB>45</SUB>Fe<SUB>30</SUB>Co<SUB>15</SUB>Al<SUB>10</SUB> alloy ribbons with various thicknesses of about 120 (N<SUB>1</SUB>) and 50 μm (N<SUB>2</SUB>) prepared by melt-spinning. Structural analyses based on an X-ray diffractometer and a high-resolution transmission electron microscope revealed an existence of nanocrystals with sizes of 10 ~ 20 nm surrounded by an amorphous host matrix. With decreasing ribbon thickness and nanocrystalline size, magnetic studies upon a vibrating sample magnetometer indicated the decrease of the Curie temperature (T<SUB>C</SUB>), coercive force (H<SUB>c</SUB>), and magnetic entropy change (ΔS<SUB>m</SUB>). In the ferromagnetic region, however, magnetization values determined for N<SUB>2</SUB> are greater than those determined for N<SUB>1</SUB>. These results are related to the differences in the critical exponents of N<SUB>1</SUB> (β=0.418 and γ=1.173), and N<SUB>2</SUB> (β=0.512 and γ=1.077), which are characteristic for the ferromagnetic nature existing in the alloy ribbons with different thicknesses.</P>
Phan, T.L.,Thanh, P.T.,Dan, N.H.,Zhang, P.,Thanh, T.D.,Phan, M.H.,Yu, S.C. Elsevier Sequoia 2014 JOURNAL OF ALLOYS AND COMPOUNDS Vol.615 No.suppl1
We have studied the magnetic and magnetocaloric (MC) properties of Ni<SUB>50-x</SUB>Pr<SUB>x</SUB>Mn<SUB>37</SUB>Sn<SUB>13</SUB> (x=0, 1, 3, and 5) alloy ingots fabricated by arc-melting. Experimental results revealed a coexistence of the conventional and inverse MC effects in the samples with x=0, 1, and 3. There is a gradual decrease of the magnetization and magnetic-entropy change (ΔS<SUB>m</SUB>) when Pr-doping content increases. However, the Curie temperature of the austenitic phase (T<SUB>C</SUB><SUP>A</SUP>) around room temperature was not changed very much. Particularly, doping a small amount of Pr with x=1 enhances remarkably the linewidth of the peaks in its ΔS<SUB>m</SUB>(T) curves. This increases the relative cooling power (RCP) of Ni<SUB>50-x</SUB>Pr<SUB>x</SUB>Mn<SUB>37</SUB>Sn<SUB>13</SUB> alloys when they are used as coolants in refrigeration devices. For example, under an applied field of H=50 kOe, the RCP increases from 150 for x=0 to ~200J/kg for x=1. Higher Pr contents reduce quickly the MC effect because of the formation of nonmagnetic secondary phases.
Magnetic Properties and Magnetocaloric Effect in Ni0.5Mn0.5.xSbx Alloys
N. H. Duc,T. D. Thanh,N. H. Yen,P. T. Thanh,N. H. Dan,판더롱 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.60 No.3
Ni0.5Mn0.5.xSbx (x = 0.1, 0.2, 0.3, and 0.4) ingots fabricated by arc-melting high-pure metals have been studied to determine their structure and magnetic properties and to identify the magnetocaloric effect. X-ray diffraction analyses reveal that the sample with x = 0.2 is close to a single phase in a cubic structure while the others have the secondary phases. This influences strongly the magnetic properties of Ni0.5Mn0.5.xSbx. With increasing Sb content, the Curie temperature (TC) increases from 210 (for x = 0.1) to 435 K (for x = 0.4). Among the studied alloys, two samples, x = 0.2 and 0.3, have the greatest saturation magnetization values, which were recorded at 300 K. Under an applied field of 12.0 kOe, the maximum magnetic entropy changes are about 1.0 and 0.5 J.kg.1·K.1 for x = 0.2 and 0.3, respectively. Detailed analyses related to isothermal M-H curves in the vicinity of TC by using the modified Arrott method reveal that these samples undergo a second-order phase transition with critical exponents of = 0.40 ± 0.01 and = 1.27± 0.08 for x = 0.2 and of = 0.69 ± 0.09 and = 0.85 ± 0.10 for x = 0.3. The differences in the critical parameters are likely related to the presence of Ni-related secondary phases.
Magnetic properties and magnetocaloric effect in Fe90-x Sn x Zr10 alloy ribbons
Phan, T. L.,Dan, N. H.,Thanh, T. D.,Mai, N. T.,Ho, T. A.,Yu, S. C.,Le, Anh-Tuan,Phan, M. H. Korean Physical Society 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.66 No.8
<P>This work points out the possibility of tuning the magnetocaloric (MC) effect in Fe90-x Sn (x) Zr-10 alloy ribbons in the temperature range from 235 to 315 K by changing the Sn-doping content (x). Under an applied field change from 0 to 50 kOe, the maximum magnetic-entropy changes around the ferromagnetic-paramagnetic phase transition are about 3.6, 4.1 and 3.3 J kg(-1)center dot K-1 for x = 0, 2 and 4, respectively, which correspond to relative cooling powers of 280 similar to 410 J center dot kg(-1). Studying the magnetic properties of the alloy ribbons based on Banerjee's criteria and assessing the magneticordering parameter n = dLn|Delta S (m) |/dLnH (where Delta S (m) and H are the magnetic-entropy change and the magnetic field, respectively) reveals that the alloys undergo a second-order phase transition and exhibit a short-range ferromagnetic order. The nature of these phenomena is further analyzed by means of the results obtained from the analyses of the crystal structure, the Curie-Weiss law, and the Griffith phase.</P>
Phan, T. L.,Manh, T. V.,Ho, T. A.,Yu, S. C.,Dan, N. H.,Yen, N. H.,Thanh, T. D. Korean Physical Society 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.11
We fabricated Huesler alloy ingots of Ni50-x Pr (x) Mn37Sn13 with x = 0 - 5 by using an arcmelting method. Crystalline-structural analyses revealed the coexistence of austenitic and martensitic phases in the samples with x = 0 and 1, in which the volume fraction of the austenitic phase for x = 1 was higher than that for x = 0. With higher Pr concentrations, x > 1, Pr- and Ni3Sn-related secondary phases, which reduced the magnetic order of the alloys, were formed. Thus, only the sample with x = 1 was more suitable for studying the critical behavior. Based on Landau's phase-transition theory and Banerjee's criteria, we found that this sample undergoes a second-order magnetic phase transition (SOMT) at a temperature around the Curie temperature T (C) a parts per thousand 299 K. Using the modified Arrott plots, asymptotic relations, and a universal scaling law, we determined the values of the critical exponents beta = 0.501 +/- 0.009 and gamma = 1.045 +/- 0.006. These values are very close to those expected for the mean-field theory with beta = 0.5 and gamma = 1, proving the existence of long-range ferromagnetic (FM) order in the sample with x = 1. Particularly, around at temperature T (C) , the magnetic-entropy change reaches the maximum value (a dagger S (max) ). Its magnetic-field dependences can be described by using a power law |a dagger S (max) | ae H (n) , where n = 0.687 is close to the value 0.677 calculated from the theoretical relation n = 1 + (beta - 1)/(beta + gamma). We believe that the doping of a suitable Pr amount in Ni50-x Pr (x) Mn37Sn13 (x a parts per thousand 1) promotes the formation of the austenitic phase and results in long-range FM order. However, the persistence of the martensitic phase and secondary phases favors short-range FM order and thus decreases the FM order in Ni50-x Pr (x) Mn37Sn13.
Maskey, S.,Chae, H.,Lee, K.,Dan, N.P.,Khoi, T.T.,Park, K. Elsevier Scientific Pub. Co 2016 Journal of hazardous materials Vol.317 No.-
Morphology and elemental composition of individual fine ambient particles varied among types of PM events and between two different urban environments having different major transportation systems (gasoline/diesel vehicles versus motorcycles). Carbonaceous particles were the most dominant in PM events, whereas S-rich particles were the highest in non-events at urban Gwangju in Korea. The aged soot, semi-volatile organic (SVO), and non-volatile organic (NVO) particles were more abundant in the polluted-long range transport (LTP) event than those in the dust-LTP event and non-event. In the dust-LTP event, the aged mineral dust particles outnumbered the fresh ones, suggesting the mineral dust particles were aged during their long-range transport. At HoChiMinh (HCM) in Vietnam, the fraction of carbonaceous particles was much higher than Gwangju (66% versus 30%) possibly due to more abundant two-stroke motor vehicles at HCM. Of the carbonaceous particles, combustion soot (19%) was the highest, followed by NVO (18%), SVO (17%), and biological particles (11%) at HCM, whereas SVO (11%) and NVO (10%) particles were the highest, followed by combustion soot particles (8%) at Gwangju. The higher fraction of mineral dust particles was also observed at HCM, indicating the sampling site was influenced by dust from unpaved roads and construction sites.
Magnetic Properties and Giant Magnetocaloric Effects on the NiMn0.9Sb0.1 Compound
Yingde Zhang,Peng Zhang,김경섭,N. H. Dan,Xueling Hou,유성초 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.61
We have studied the magnetization behavior and the magnetocaloric effect for the NiMn0.9Sb0.1 Heusler alloy. The sample was prepared by arc-melting in an argon atmosphere. For homogeneity of the samples, the ingot was melted several times. The temperature dependence of the magnetization of the sample was measured using a vibrating sample magnetometer in the magnetic field range up to 10 kOe. A large entropy change was observed from the H versus M curves associated with the ferromagnetic-paramagnetic transition. The maximum entropy change was 2.36 J/kg K at 697.5 K. Our results indicate that the present NiMn0.9Sb0.1 alloy is a good candidate as working material for a magnetic refrigerant.
Zhang, P.,Phan, T.L.,Dan, N.H.,Thanh, T.D.,Yu, S.C. Elsevier Sequoia 2014 Journal of alloys and compounds Vol.615 No.suppl1
The magnetic phase transition behavior were investigated in detail in Ni<SUB>50-y</SUB>Gd<SUB>y</SUB>Mn<SUB>37</SUB>Sn<SUB>13</SUB> (y=1 and 3) alloys prepared by arc-melting method. The martensite phase was found to be strongly suppressed by a small amount of Gd doping. Based on isothermal magnetization curves around Curie temperature of the austenite (T<SUB>C</SUB><SUP>A</SUP>) phase, critical behavior in the austenite phases of both alloys were determined carefully by the Kouvel-Fisher method. The critical exponents were found to be β=0.473+/-0.020 and γ=1.141+/-0.017 with T<SUB>C</SUB><SUP>A</SUP>=299.0+/-0.2K for y=1, and β=0.469+/-0.068 and γ=1.214+/-0.042 with T<SUB>C</SUB><SUP>A</SUP>=302.9+/-0.7K for y=3, respectively. The values of the critical exponents for the ferromagnetic phase transition in the A phase of two alloys can be basically ascribed in the mean-field model (with β=0.5, γ=1) with slightly deviation, revealing a long-range order of ferromagnetic interactions. Such critical behavior can be attributed to the magnetic inhomogeneities originated from the atomic disorder introduced by Gd doping.