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Magnetoresistance Effect in La1.5Sr0.5NiO4-Doped La0.7Ca0.3MnO3 Nanocomposites
Thanh, Tran Dang,Van, Hoang Thanh,Lee, Jong Suk,Yu, Seong-Cho Springer-Verlag 2017 Journal of superconductivity and novel magnetism Vol.30 No.3
<P>Our experimental results point out that most La1.5Sr0.5NiO4 nanoparticles were distributed at the grain boundaries and on the surfaces of the La0.7Ca0.3MnO3 nanoparticles. The nanocomposite samples exhibit a ferromagnetic-paramagnetic and a metal-insulator phase transitions at T (C) and T (MI), respectively. With increasing La1.5Sr0.5NiO4-doped content, T (C) value is almost unchanged while T (MI) value decreases from 251 K for an undoped sample to 65 K for 20 % La1.5Sr0.5NiO4-doped one. Particularly, the La1.5Sr0.5NiO4-doped samples higher than 20 % exhibit the insulating properties in the whole temperature range. Magnetoresistance effect at low field (H= 3 kOe) of all the samples is observed. In order to explore the nature of their magnetoresistance effect at low field according to temperature and magnetic field change, we analyzed carefully the obtained data based on the phenomenological model related to the spinpolarized transport of conduction electrons at grain boundaries. With this, the temperature dependences of magnetoresistances (including the intrinsic magnetoresistances and spinpolarized transport magnetoresistances) can be described well by an expression of the Curie-Weiss law-like behavior, a + b/(c + T). We also have been able to observe the percolation threshold in this system for 25 % of La1.5Sr0.5NiO4 component, and around this critical point a great increase of magnetoresistances has been detected.</P>
Magnetic Properties and Magnetocaloric Effect at Room Temperature of Ni50−xAgxMn37Sn13 Alloys
Tran Dang Thanh,Nguyen Thi Mai,Nguyen Huy Dan,The-Long Phan,유성초 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.10
In this work, we present a detailed study of the magnetic properties and the magnetocaloric effectat room temperature of Ni50−xAgxMn37Sn13 alloys with x = 1, 2, and 4, which were prepared byusing an arc-melting method. Experimental results reveal that a partial replacement of Ag for Nileads to a decrease in the anti-FM phase in the alloys. In addition, the martensitic-austenitic phasetransition shifts towards lower temperature and is broaded. The Curie temperature (TAC ) for theaustenitic phase also shifts toward to lower temperature, but not by much. The Curie temperaturewas found to be 308, 305, and 298 K for x = 1, 2, and 4, respectively. The magnetic entropychange (Sm) of the samples was calculated by using isothermal magnetization data. Under anapplied magnetic field change of 10 kOe, the maximum value of Sm (|Smax|) was achieved ataround room temperature and did not change much (0.8 J·kg−1·K−1) with increasing Ag-dopingconcentration. Particularly, the M2 vs. H/M curves prove that all the samples exhibited a secondordermagnetic phase transition. Based on Landau’s phase-transition theory and careful analyses ofthe magnetic data around the TAC , we have determined the critical parameters ,, , and TC. Theresults show that the values are located between those expected for the 3D-Heisenberg model (= 0.365) and mean-field theory ( = 0.5). Such a result proves the coexistence of short-range andlong-range ferromagnetic interactions in Ni50−xAgxMn37Sn13 alloys. The nature of the changes inthe critical parameters and the |Smax| is thoroughly discussed by means of structural analyses.
Tran Dang Thanh,Phan, T. L.,Le Mai Oanh,Nguyen Van Minh,Jong Suk Lee,Yu, S. C. IEEE 2014 IEEE transactions on magnetics Vol.50 No.6
<P>This paper presents the influence of Mn doping on the structural characterization, and optical and magnetic properties of SrTi<SUB>1-x</SUB>Mn<SUB>x</SUB>O<SUB>3</SUB>(x = 0.0-0.1) materials prepared by a solid-state reaction method. The detailed analyses of X-ray diffraction patterns indicate an incorporation of Mn dopants into Ti sites of the SrTiO<SUB>3</SUB> host lattice. There is a cubic to tetragonal transformation, which takes place at a threshold concentration x ≈ 0.04. The optical absorption spectra show a rapid increase in the absorption coefficient. The bandgap energy (Eg) related to the direct electron transition decreases with increasing Mn concentration: Eg decreases from 3.15 eV for x = 0 to 1.28 eV for x = 0.10. From this point of view, the SrTi<SUB>1-x</SUB>Mn<SUB>x</SUB>O<SUB>3</SUB> materials are considered as promising materials for photocatalytic applications. Interestingly, while the samples with x = 0.0-0.02 are diamagnetic, the others with x = 0.04-0.10 exhibit weak ferromagnetism. The ferromagnetic order increases with increasing Mn concentration. Based on the results of structural and optical analyses, the nature of magnetism in the samples is explained thoroughly.</P>
Tran Dang Thanh,Phan, T. L.,Phung Quoc Thanh,Hoang Nam Nhat,Duong Anh Tuan,Yu, S. C. IEEE 2014 IEEE transactions on magnetics Vol.50 No.6
<P>This paper presents a detailed study on the Co-doping influence on the electrical and magnetotransport properties of La0.7Ca0.3Mn1-xCoxO3(x = 0.09-0.17) prepared by solid-state reaction. Magnetic measurements versus temperature revealed a gradual decrease of the magnetization (M) and Curie temperature (T-C) with increasing Co concentration (x). The T-C values vary from 194 to 159 K as changing x from 0.09 to 0.17, respectively. H/M versus M-2 performances around T-C prove the x = 0.09 sample undergoing a first-order magnetic phase transition (FOMT) while the samples with x >= 0.11 undergo a second-order magnetic phase transition (SOMT). The other with x = 0.10 is considered as a threshold concentration of the FOMT-SOMT transformation. Considering temperature dependences of resistivity, rho(T), in the presence and absence of the magnetic field, the samples (excepting for x = 0.17) exhibit a metal-insulator transition at T (P) = 60-160 K, which shifts toward lower temperatures with increasing x. In the metallic-ferromagnetic region, the rho(T) data are well fitted to a power function rho(T) = rho(0) + rho(2) T-2 + rho(4.5) T-4.5. This indicates electron-electron and electron-magnon scattering processes are dominant at temperatures T < T (P). In addition, the conduction data at temperatures T > theta(D)/2 (theta(D) is the Debye temperature) and T (P) < T < theta(D)/2 obey the small-polaron and variable-range hopping models, respectively. The values of activation energy E-p, and density of states at the Fermi level N(E-F) were accordingly determined. Here, N(E-F) increases while E-p decreases when an external magnetic field is applied. We also have found that N(E-F) increases when materials transfer from the FOMT to the SOMT, and N(E-F) value becomes smallest for the sample having the coexistence of the FOMT and SOMT (i.e., x = 0.10).</P>
AC and DC Conductivity of Multiferroic La2-xSrxNiO4+??
Tran Dang Thanh,Le Van Hong 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5
The DC and AC, up to 1 MHz, conductivity, the thermo-magnetization and the magnetic hysteresis of the La2..xSrxNiO₄+δ polycrystalline ceramic were measured and estimated over a wide temperature range from 20 K to 300 K. The obtained results show that La2..xSrxNiO₄+δ is multiferroic. In the DC region measurement the samples exhibit a semiconductor-like behavior with the activation energy decreasing with increasing Sr concentration. Clear evidence of charge ordering and spin ordering are observed around temperatures of 75 K and 200 K in samples doped with Sr at concentrations below 15 % (x < 0:3). The AC conductivity exhibits a change in conducting behavior at a peak temperature, Tp, near Tco and depends on frequency, which should be related to a change in the stripe structure of the nickelate, as well as to the multiferroic behavior of this material. The DC and AC, up to 1 MHz, conductivity, the thermo-magnetization and the magnetic hysteresis of the La2..xSrxNiO₄+δ polycrystalline ceramic were measured and estimated over a wide temperature range from 20 K to 300 K. The obtained results show that La2..xSrxNiO₄+δ is multiferroic. In the DC region measurement the samples exhibit a semiconductor-like behavior with the activation energy decreasing with increasing Sr concentration. Clear evidence of charge ordering and spin ordering are observed around temperatures of 75 K and 200 K in samples doped with Sr at concentrations below 15 % (x < 0:3). The AC conductivity exhibits a change in conducting behavior at a peak temperature, Tp, near Tco and depends on frequency, which should be related to a change in the stripe structure of the nickelate, as well as to the multiferroic behavior of this material.
Tran Ha Thi Thanh,Dang Anh Kieu,Ly Duc Viet,Vu Hao Thi,Hoang Tuan Van,Nguyen Chinh Thi,Chu Nhu Thi,Nguyen Vinh The,Nguyen Huyen Thi,Truong Anh Duc,Pham Ngoc Thi,Dang Hoang Vu 아세아·태평양축산학회 2020 Animal Bioscience Vol.33 No.10
Objective: The rapid and reliable detection of the African swine fever virus (ASFV) plays an important role in emergency control and preventive measures of ASF. Some methods have been recommended by FAO/OIE to detect ASFV in clinical samples, including real-time polymerase chain reaction (PCR). However, mismatches in primer and probe binding regions may cause a false-negative result. Here, a slight modification in probe sequence has been conducted to improve the qualification of real-time PCR based on World Organization for Animal Health (OIE) protocol for accurate detection of ASFV in field samples in Vietnam. Methods: Seven positive confirmed samples (four samples have no mismatch, and three samples contained one mutation in probe binding sites) were used to establish novel real-time PCR with slightly modified probe (Y = C or T) in comparison with original probe recommended by OIE. Results: Both real-time PCRs using the OIE-recommended probe and novel modified probe can detect ASFV in clinical samples without mismatch in probe binding site. A high correlation of cycle quantification (Cq) values was observed in which Cq values obtained from both probes arranged from 22 to 25, suggesting that modified probe sequence does not impede the qualification of real-time PCR to detect ASFV in clinical samples. However, the samples with one mutation in probe binding sites were ASFV negative with OIE recommended probe but positive with our modified probe (Cq value ranked between 33.12-35.78). Conclusion: We demonstrated for the first time that a mismatch in probe binding regions caused a false negative result by OIE recommended real-time PCR, and a slightly modified probe is required to enhance the sensitivity and obtain an ASF accurate diagnosis in field samples in Vietnam.
Conventional and inverse magnetocaloric effects, and critical behaviors in Ni43Mn46Sn8In3 alloy
Tran Dang Thanh,W.Z. Nan,Gnu Nam,Hoang Thanh Van,유태수,판더롱,S. C. Yu 한국물리학회 2015 Current Applied Physics Vol.15 No.10
A systematic study of the conventional and inverse magnetocaloric effects, and critical behaviors in an alloy ingot of Ni43Mn46Sn8In3 has been performed. Our results reveal the sample exhibiting structural and magnetic phase transitions at temperatures TC M = 166 K (TC of the martensitic phase), TM-A =260 K (the martensitic-to-austenitic phase transformation) and TC A = 296 K (TC of the austenitic phase). The large values of refrigerant capacity (RC) around TMeA and TC A are found to be RCM-A = 172.6 and RCA = 155.9 J kg-1, respectively, under an applied field change of 30 kOe. Our critical analyses near the TC M and TC A reveal that a coexistence of the long- and short-range ferromagnetic order in the martensitic phase, while the long-range ferromagnetic order exists in the austenitic phase. Interestingly, at around TC A, the maximum magnetic entropy change (|ΔSmax|) versus magnetic field H obeys a power law, |ΔSmax| = a·Hn, where the exponent n is found to be about 0.66.