 Article
Authors: Phung, ThanhPQ (2014)  We used Banerjee0
s criteria, modified Arrott plots, and the scaling hypothesis to analyze magneticfield dependences of magnetization near the ferromagnetic–paramagnetic (FM–PM) phasetransition temperature (TC) of perovskitetype manganites La0.7Ca0.3Mn1 x
NixO3(x¼0.09, 0.12 and
0.15). In the FM region, experimental results for the critical exponentβ(¼0.171 and 0.262 for
x¼0.09 and 0.12, respectively) reveal twofirst samples exhibiting tricriticality associated with the
crossover offirst and secondorder phase transitions. Increasing Nidoping content leads to the
shift of theβvalue (¼0.320 forx¼0.15) towards that expected for the 3D Ising model (β¼0.325).
This is due to the fact that the substitution of Ni ions into the Mn site changes structural parameters
and dilutes the...

 Article
Authors: Phung, ThanhPQ (2006)  Amorphous soft magnetic ribbons Fe73.5 xCrxSi13.5B9Nb3Cu1
(x¼1–5) have been fabricated by rapid quenching on a single copper
wheel. The differential scanning calorimetry (DSC) patterns showed that the crystallization temperature ofaFe(Si) phase is ranging
from 542 to 5691C, a little higher than that of pure Finemet (x¼0). With the same annealing regime, the crystallization volume fraction
as well as the particle size ofaFe(Si) crystallites decreased with increasing Cr amount substituted for Fe in studied samples. Especially,
the interesting fact is that the laminar structure of heattreated ribbons on the surface contacted to copper wheel in the fabricating
process has been firstly discovered and explained to be related to the existence of Cr in studied samples. The hysteres...

 Article
Authors: Phung, ThanhPQ (2004)  Ca1 xPrxMnO3 d (x=0, 0.05, 0.15, 0.1, 0.2, 0.4, 0.67;d=0.02) samples were prepared by a solidstate reaction
method. Xray diffraction analysis showed that all samples prepared were of single phase with orthorhombic structure.
Electrical resistivity measurements from room temperature to 1300 K showed that a metallic conducting tendency
dominated at high temperatures. The hopping nature of the charge carriers was well interpreted in the framework of
polaron theory. The Seebeck coefficient was measured in the same temperature interval, and its concentration
dependence was analyzed using the hightemperature (HT) thermopower theory proposed by Marsh–Parris. The
thermal conductivity and the figure of merit of the prepared samples were also compared with those of other similar
per...

 Article
Authors: Phung, ThanhPQ (201204)  We have studied the influence of the Cudoping on the critical properties of a polycrystalline sample of
prepared by solidstate reaction. Analyses of static magnetization data in the vicinity of the ferromagneticparamagnetic phase transition based on the modified Arrott plot reveal critical parameters of
, and .These parameters are in good agreement with a magnetic equation of state
, where
(the reduced temperature), for and for . Comparing with theoretical models, the critical exponents in our
case are close to those expected for the meanfield theory. This reflects that the Cu doping leads to the secondorder phase transition in while the parent compound of exhibits the firstorder phase...

 Article
Authors: Phung, ThanhPQ (2007)  The excellent agreement with experimental data has been achieved in fitting the resistivity of doped manganate–ruthenates for whole temperature range. The analysis interpreted the resistivity in terms of percolation of carriers through the system of grain boundaries, having been assumed as the conductive fractal medium. The percolative conduction regime has been shown substantial for the Kdoped
ruthenates [H.N. Nhat, H.D. Chinh and M.H. Phan, Solid State Commun. 139 (2006) 456], and we confirm here that this approach also correctly discusses the unusual semiconductorlike behaviours of the doped manganate–ruthenates

 Article
Authors: Phung, ThanhPQ (2013)  We have studied the critical behavior and magnetocaloric effect of a perovskitetype manganite
LaMn0.9Fe0.1O3with a secondorder phase transition. Detailed critical analyses based on the modified
Arrott plot method and the universal scaling law gave the critical parameters TC≈135.7 K,
β¼0.35870.007, γ¼1.32870.003, and δ¼4.7170.06. Comparing to standard models, the critical
exponent values determined in our work are close to those expected for the 3D Heisenberg model
(withβ¼0.365,γ¼1.336, andδ¼4.80). This reflects an existence of ferromagnetic shortrange order in
LaMn0.9Fe0.1O3. Around TC, the magnetic entropy change reaches the maximum value (ΔSmax), which is
about 3.8 J kg−1 K−1 for the appliedfield of 50 kOe. Particularly, its magneticfield dependence obeys the
power law...

 Article
Authors: Phung, ThanhPQ (2007)  Singlephase perovskite compounds Ca0.6Pr0.4Mn1 yRuyO3 (y¼0, 0.03, 0.05, 0.07) were prepared by ceramictechnology method. Thermomagnetic plots, temperature dependence of resistivities, acsusceptibilities of the produced samples were determined. The nonruthenium doping (y¼0) sample presents chargeordering phenomenon at TCO¼291 K. The experiment results show that the ruthenium doping destroys the charge ordering state, enhances ferromagnetism tendency and conductivity

 Article
Authors: Phung, ThanhPQ (201211)  CaMnO3 is an antiferromagnet, in which the superexchange interaction taking place between
Mn4+ ions plays an important role. The doping of a small amount of 15% Pr into the Ca site,
Ca0.85Pr0.15MnO3, leads to the appearance of Mn3+ ions, and introduces the ferromagnetic (FM)
doubleexchange interaction between Mn3+ and Mn4+ ions, which is dominant in a narrow temperature range of 90 ∼ 115 K. The FM interaction becomes strong for Ca0.85Pr0.15MnO3 doped with
4 and 8% Ru into the Mn site (i.e., Ca0.85Pr0.15Mn1−xRuxO3 with x = 0.04 and 0.08). The Curie
temperature obtained for x = 0.04 and 0.08 are about 135 and 180 K, respectively. While the FM
interaction in the former is dominant due to Mn3+Mn4+ exchange pairs, the latter has the contribution of Ru ions. This results in remar...

 Other
Authors: Phung, ThanhPQ (201511)  

 Article
Authors: Phung, ThanhPQ (2012)  The magnetic and transport properties of the perovskites La0.67Ca0.33Mn1xTMxO3 were found to be
sufficiently changed with the substitution of Mnsites by other 3d transitionmetal cations (TM¼Cu,Zn;
x¼0.15). The values ofTC, TM I, and TCMRwere surveyed when Mn was replaced by Cu and Zn. The
magnetic field induced resistivity and magnetic entropy change of these samples showed abrupt
changes nearTC(194.2 and 201.5 K for Cu and Zndoped case respectively) and attained the highest
values among the doped cases (up to 20% Cu). The maximum values (obtained at H¼4 kOe) of
magnetoresistance ratio (CMR) were 27.8%, and 24.5% and of magnetic entropy change ( DSM)were
3.9 and 3.2 J/kg K for Cu and Zndoped, respectively
