다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

The response of the worldwide scientific community to the discovery in 2008 of superconductivity at T c = 26 K in the Fe-based compound LaFeAsO1−x F x has been very enthusiastic. In short order, ot...

The puzzle of high temperature superconductivity in layered iron pnictides and chalcogenides

The article tells about the diversity of green spaces in London, the citizens’ attitude toward these spaces, and what Russian cities can learn from this experience.

Nature in London

H E Stanley Oxford: University Press 1971 pp xx + 308 price ?5 In the past fifteen years or so there has been a lot of experimental and theoretical work on the nature of critical phenomena in the neighbourhood of second order phase transitions. It has not been easy to get a good overall view of this work without digging through the rather complex original literature, although there are some good review articles covering particular aspects of the work.

https://iopscience.iop.org/article/10.1088/0031-9112/23/4/018/pdf

Introduction to Phase Transitions and Critical Phenomena

A review on nanostructured carbon quantum dots and their applications in biotechnology, sensors, and chemiluminescence.

The critical behavior at the paramagnetic to ferromagnetic phase transition in ${\text{Pr}}_{0.5}{\text{Sr}}_{0.5}{\text{MnO}}_{3}$ is studied using techniques such as modified Arrott plot, Kouvel-Fisher plot, and critical isotherm analysis. Though the nature of this transition is found to be of second order, the estimated critical exponents $\ensuremath{\beta}$, $\ensuremath{\gamma}$, and $\ensuremath{\delta}$ are in between the theoretically predicted values for three-dimensional Heisenberg and mean-field interaction models. However, it is noteworthy that the scaling relations are obeyed indicating renormalization of interactions around the Curie temperature $({T}_{C})$. Temperature variation in effective exponents (${\ensuremath{\beta}}_{\text{eff}}$ and ${\ensuremath{\gamma}}_{\text{eff}}$) resemble with those for disordered ferromagnet. It is shown that fully localized-spin interaction models are not applicable for this compound, and ferromagnetic interaction has itinerant character. Moreover, the exponents determined in this study are close to those calculated from the results of renormalization group approach for a heuristic model of two-dimensional Heisenberg spins coupled with long-range interaction. These results suggest that critical phenomenon in ${\text{Pr}}_{0.5}{\text{Sr}}_{0.5}{\text{MnO}}_{3}$, which is found to be an inhomogeneous ferromagnet around ${T}_{C}$, could not be described within the framework of existing universality classes and probably belong to a separate class.

Critical behavior at paramagnetic to ferromagnetic phase transition in Pr 0.5 Sr 0.5 MnO 3 : A bulk magnetization study

We show Griffiths phase (GP)-like behavior in half-doped ${\text{Pr}}_{0.5}{\text{Sr}}_{0.5}{\text{MnO}}_{3}$ having ferromagnetic (FM) spin correlation above FM transition $({T}_{C})$ without any spontaneous magnetization. Temperature range and exponent of GP increase with Ga substitution at Mn site which is not related with structural disorder as Ga does not affect the structure, moreover, reduces Jahn-Teller active ${\text{Mn}}^{3+}$ ions. FM clusters both above and below ${T}_{C}$ reduces their size with Ga. Hence, it is considered that GP originates from phase inhomogeneity and evolves with addition of disorder due to change in its length scale.

Griffiths phase and its evolution with Mn-site disorder in the half-doped manganite Pr 0.5 Sr 0.5 Mn 1 − y Ga y O 3 ( y = 0.0 , 0.025, and 0.05)

Coexisting ferromagnetic and antiferromagnetic phases over a range of temperature as well as magnetic field have been reported in many materials of current interest, showing disorder-broadened first-order transitions. Anomalous history effects observed in magnetization and resistivity are being explained invoking the concepts of kinetic arrest akin to glass transitions. From magnetization measurements traversing unusual paths in field-temperature space, we obtain the intriguing result that the regions of the sample which can be supercooled to lower temperatures undergo kinetic-arrest at higher temperatures, and vice versa. Our results are for two diverse systems viz., the inter-metallic doped $\mathrm{Ce}{\mathrm{Fe}}_{2}$ which has an antiferromagnetic ground state, and the oxide La-Pr-Ca-Mn-O which has a ferromagnetic ground state, indicating the possible universality of this effect of disorder on the widely encountered phenomenon of glass-like arrest of kinetics.

Relating supercooling and glass-like arrest of kinetics for phase separated systems: Doped CeFe 2 and (La,Pr,Ca)MnO 3

In-situ synthesis of rGO-ZnO nanocomposite for demonstration of sunlight driven enhanced photocatalytic and self-cleaning of organic dyes and tea stains of cotton fabrics.

The nature of phase separation in Pr0.5Sr0.5MnO3 has been probed by linear, as well as nonlinear, magnetic susceptibilities and resistivity measurements across the second order paramagnetic to ferromagnetic transition (TC) and first order ferromagnetic to antiferromagnetic transition (TN). We found that the ferromagnetic (metallic) clusters, which form at TC, continuously decrease their size with a decrease in temperature and coexist with non-ferromagnetic (insulating) clusters. These non-ferromagnetic clusters are identified to be antiferromagnetic. It is shown that they do not arise because of the superheating effect of the lower temperature first order transition. This reveals phase coexistence in manganite, around half-doping, encompassing two long-range order transitions. Substitution of quenched disorder (Ga) at Mn-sites promotes antiferromagnetism at the cost of ferromagnetism without adding any magnetic interaction or introducing any significant lattice distortion. Moreover, an increase in disorder decreases the ferromagnetic cluster size and with 7.5% Ga substitution cluster size reduces to the single-domain limit. Resistivity measurements also reveal the phase coexistence identified from the magnetic measurements. It is significant that, an increase in disorder up to 7.5% increases the resistivity of the low temperature antiferromagnetic phase by about four orders.

Ashim Pramanik

Papers

Critical behavior at paramagnetic to ferromagnetic phase transition in Pr 0.5 Sr 0.5 MnO 3 : A bulk magnetization study

Griffiths phase and its evolution with Mn-site disorder in the half-doped manganite Pr 0.5 Sr 0.5 Mn 1 − y Ga y O 3 ( y = 0.0 , 0.025, and 0.05)

Relating supercooling and glass-like arrest of kinetics for phase separated systems: Doped CeFe 2 and (La,Pr,Ca)MnO 3

In-situ synthesis of rGO-ZnO nanocomposite for demonstration of sunlight driven enhanced photocatalytic and self-cleaning of organic dyes and tea stains of cotton fabrics.

Phase separation and the effect of quenched disorder in Pr0.5Sr0.5MnO3