scholarly journals First-order antiferromagnetic transitions of SrMn2P2 and CaMn2P2 single crystals containing corrugated-honeycomb Mn sublattices

2021 ◽  
Vol 118 (44) ◽  
pp. e2108724118
Author(s):  
N. S. Sangeetha ◽  
Santanu Pakhira ◽  
Qing-Ping Ding ◽  
Lennard Krause ◽  
Hyung-Cheol Lee ◽  
...  
Keyword(s):  
Heat Capacity ◽  
Magnetic Susceptibility ◽  
Single Crystals ◽  
Nearest Neighbor ◽  
Second Order ◽  
Magnetic Structures ◽  
First Order ◽  
Slowing Down ◽  
First Order Transition ◽  
Antiferromagnetic Transitions

SrMn2P2 and CaMn2P2 are insulators that adopt the trigonal CaAl2Si2-type structure containing corrugated Mn honeycomb layers. Magnetic susceptibility χ and heat capacity versus temperature T data reveal a weak first-order antiferromagnetic (AFM) transition at the Néel temperature TN=53(1) K for SrMn2P2 and a strong first-order AFM transition at TN=69.8(3) K for CaMn2P2. Both compounds exhibit isotropic and nearly T-independent χ(T≤TN), suggesting magnetic structures in which nearest-neighbor moments are aligned at ≈120° to each other. The 31P NMR measurements confirm the strong first-order transition in CaMn2P2 but show critical slowing down above TN for SrMn2P2, thus also evidencing second-order character. The 31P NMR measurements indicate that the AFM structure of CaMn2P2 is commensurate with the lattice whereas that of SrMn2P2 is incommensurate. These first-order AFM transitions are unique among the class of (Ca, Sr, Ba)Mn2 (P, As, Sb, Bi)2 compounds that otherwise exhibit second-order AFM transitions. This result challenges our understanding of the circumstances under which first-order AFM transitions occur.

First-Order Transition in anxyModel with Nearest-Neighbor Interactions

1984 ◽  
Vol 52 (17) ◽  
pp. 1535-1538 ◽  
Author(s):  
Eytan Domany ◽  
Michael Schick ◽  
Robert H. Swendsen
Keyword(s):  
Nearest Neighbor ◽  
Order Transition ◽  
First Order ◽  
First Order Transition

A study of the first-order valence transition in single crystals by magnetic susceptibility measurements

1999 ◽  
Vol 11 (2) ◽  
pp. 543-554 ◽  
Author(s):  
D T Adroja ◽  
Y Echizen ◽  
T Takabatake ◽  
Y Matsumoto ◽  
T Suzuki ◽  
...  
Keyword(s):  
Magnetic Susceptibility ◽  
Single Crystals ◽  
Valence Transition ◽  
First Order

Glass-Formers and Viscous Liquid Slowdown since David Turnbull: Enduring Puzzles and New Twists

MRS Bulletin ◽  
2008 ◽  
Vol 33 (5) ◽  
pp. 544-555 ◽  
Author(s):  
C.A. Angell
Keyword(s):  
Heat Capacity ◽  
Glass Transition ◽  
Free Volume ◽  
Homogeneous Nucleation ◽  
Liquid Metals ◽  
Order Transition ◽  
Heat Capacity Change ◽  
Pure Liquid ◽  
First Order ◽  
First Order Transition

AbstractTo Turnbull's study of the kinetic problem of nucleation and growth of crystals, we add the further enquiry into what lies behind the slow nucleation kinetics of glass-formers. Our answer to this question leads to the proposal of conditions in which a pure liquid metal, monatomic and elemental, can be vitrified. Using the case of high-pressure liquid germanium, we give electron microscope evidence for the validity of our thinking.On the question of how liquids behave when crystals do not form, Turnbull pioneered the study of glass transitions in metallic alloys, measuring the heat capacity change at the glass transition Tg for the first time, and developing with Cohen the free volume model for the temperature dependence of liquid transport properties approaching Tg. We extend the phenomenological picture to include networks where free volume does not play a role and reveal a pattern of behavior that provides for a classification of glass-formers (from “strong” to “fragile”). Where Turnbull studied supercooled liquid metals and P4 to the homogeneous nucleation limit using small droplets, we studied supercooled water in capillaries and emulsions to the homogeneous nucleation limit near −40°C. We discuss the puzzling divergences observed that are now seen as part of a cooperative transition that leads to very untypical glass-transition behavior at lower temperatures (when crystallization is bypassed by hyperquenching). Finally, we show how our interpretation of water behavior can be seen as a bridge between the behavior of the “strong” (network) liquids of classical glass science (e.g., SiO2) and the “fragile” behavior of typical molecular glass-formers. The link is made using a “Gaussian excitations” model by Matyushov and the author in which the spike in heat capacity for water is pushed by cooperativity (disorder stabilization of excitations) into a first-order transition to the ground state, at a temperature typically below Tg. In exceptional cases like triphenyl phosphite, this liquid-to-glass first-order transition lies above Tg and can be studied in detail.

A Calorimetric Study of Ammonium, Rubidium, and Potassium Hexafluophosphate

1963 ◽  
Vol 18 (2) ◽  
pp. 148-154 ◽  
Author(s):  
L. A. K. Staveley ◽  
N. R. Grey ◽  
M. J. Layzell
Keyword(s):  
Heat Capacity ◽  
Low Temperatures ◽  
Potassium Salt ◽  
Room Temperature ◽  
Entropy Change ◽  
Ammonium Ion ◽  
Calorimetric Study ◽  
First Order ◽  
Rubidium Salt ◽  
First Order Transition

Measurements have been made of the heat capacities of ammonium, rubidium, and potassium hexafluophosphate from ∼ 20°K to ∼ 300°K. The heat capacity curve of the ammonium salt shows two anomalous regions, and an order-disorder change also occurs in the rubidium salt. The potassium salt, however, undergoes a first-order transition with a large entropy change. The heat capacity of the ammonium and rubidium salts in the neighbourhood of room temperature (but not that of the potassium salt) is altered by cooling to low temperatures. In certain ranges of temperature it was unusually difficult with the rubidium salt to obtain reproducible heat capacity values. The results show that the rotation of the ammonium ion is not completely free, but they are consistent with almost free rotation in one degree of freedom and partially restricted rotation in the other two. The possible significance of the entropy changes of the various transitions is briefly discussed.

scholarly journals Heisenberg spins on an anisotropic triangular lattice: PdCrO2 under uniaxial stress

2021 ◽  
Author(s):  
Dan Sun ◽  
Dmitry Sokolov ◽  
Richard Waite ◽  
Seunghyun Khim ◽  
Pascal Manuel ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Triangular Lattice ◽  
Ground State ◽  
Nearest Neighbor ◽  
Magnetic Order ◽  
Uniaxial Stress ◽  
Rate Of Change ◽  
Resistivity Measurements ◽  
First Order ◽  
First Order Transition

Abstract When Heisenberg spins interact antiferromagnetically on a triangular lattice and nearest-neighbor interactions dominate, the ground state is 120◦ antiferromagnetism. In this work, we probe the response of this state to lifting the triangular symmetry, through investigation of the triangular antiferromagnet PdCrO2 under uniaxial stress by neutron diffraction and resistivity measurements. The periodicity of the magnetic order is found to change rapidly with applied stress; the rate of change indicates that the magnetic anisotropy is roughly forty times the stress-induced bond length anisotropy. At low stress, the incommensuration period becomes extremely long, on the order of 1000 lattice spacings; no locking of the magnetism to commensurate periodicity is detected. Separately, the magnetic structure is found to undergo a first-order transition at a compressive stress of ∼0.4 GPa, at which the interlayer ordering switches from a double- to a single-q structure.

scholarly journals Исследование фазовых переходов и термодинамических свойств модели Поттса с C-=SUB=-q-=/SUB=-=4 на гексагональной решетке с взаимодействиями вторых ближайших соседей

2020 ◽  
Vol 62 (3) ◽  
pp. 442
Author(s):  
М.К. Рамазанов ◽  
А.К. Муртазаев ◽  
М.А. Магомедов ◽  
М.К. Мазагаева
Keyword(s):  
Phase Transitions ◽  
Hexagonal Lattice ◽  
Magnetic Ordering ◽  
Nearest Neighbors ◽  
Magnetic Structures ◽  
First Order ◽  
The Monte Carlo Method ◽  
Cumulant Method ◽  
First Order Transition ◽  
Fourth Order Cumulant

Magnetic structures of the ground state, phase transitions and thermodynamic properties of the 2D ferromagnetic Potts model with the number of spin states q = 4 on a hexagonal lattice with next-nearest neighbors interactions are investigated by the Monte Carlo method based on the Wang-Landau algorithm. It is shown that taking into account the antiferromagnetic interactions of the next-nearest neighbors leads to the appearance of frustration and a violation of magnetic ordering. The orders of the phase transitions are investigated using the Binder fourth-order cumulant method and histogram analysis of data. It is established that a first-order transition is observed in the model being investigated.

Electrical properties of MEM(TCNQ)2

1980 ◽  
Vol 58 (3) ◽  
pp. 334-342 ◽  
Author(s):  
M. Morrow ◽  
W. N. Hardy ◽  
J. F. Carolan ◽  
A. J. Berlinsky ◽  
Larry Weiler ◽  
...  
Keyword(s):  
Activation Energy ◽  
Heat Capacity ◽  
Dielectric Constant ◽  
Coulomb Interactions ◽  
One Dimensional ◽  
First Order ◽  
Nmr Data ◽  
First Order Transition ◽  
Electrical Data

Detailed studies of the dc and microwave conductivity and dielectric constant of the quasi-one-dimensional conductor, MEM(TCNQ)2 for 4.2 K < T < 360 K are presented. Particular attention is paid to the strong first-order transition at 335 K where the conductivity jumps by about three orders of magnitude on heating and the activation energy for the conductivity disappears. These electrical data are compared to previously published magnetic susceptibility measurements and to recent structural, heat capacity, and nmr data. The role of Coulomb interactions, in determining the temperature dependence of the conductivity, the susceptibility, and the structure, is emphasized.

scholarly journals Morin-type transition in 5C pyrrhotite

2020 ◽  
Vol 105 (9) ◽  
pp. 1404-1411
Author(s):  
Charles R.S. Haines ◽  
Giulio I. Lampronti ◽  
Wim T. Klooster ◽  
Simon J. Coles ◽  
Sian E. Dutton ◽  
...  
Keyword(s):  
Heat Capacity ◽  
Magnetic Hysteresis ◽  
Hysteresis Loops ◽  
Theoretical Treatment ◽  
X Ray Diffraction ◽  
Resonant Ultrasound Spectroscopy ◽  
Magnetic Structures ◽  
Vacancy Ordering ◽  
First Order Transition ◽  
Resonant Ultrasound

Abstract We report the discovery of a low-temperature spin-flop transition in 5C pyrrhotite at ~155 K that is similar to those seen in hematite at 260 K and FeS (troilite) at 440 K. The 5C crystal was produced by annealing a 4C pyrrhotite crystal at 875 K to produce a change in the vacancy-ordering scheme that developed during cooling. The 5C structure is confirmed by single-crystal X-ray diffraction and the stoichiometry and homogeneity by electron microprobe and SEM BSE mapping. Resonant ultrasound spectroscopy (RUS), heat capacity, and magnetization measurements from room temperature down to 2 K are reported. The transition is marked by a steep change in elastic properties at the transition temperature, a peak in the heat capacity, and weak anomalies in measurements of magnetization. Magnetic hysteresis loops and comparison with the magnetic properties of 4C pyrrhotite suggest that the transition involves a change in orientation of moments between two different antiferromagnetic structures, perpendicular to the crystallographic c-axis at high temperatures and parallel to the crystal-lographic c-axis at low temperatures. The proposed structures are consistent with a group theoretical treatment that also predicts a first-order transition between the magnetic structures.

Sign in / Sign up

Export Citation Format

Share Document