scholarly journals Quantum criticality in a three-dimensional spin system at zero field and pressure

2017 ◽  
Vol 96 (14) ◽  
Author(s):  
K. Yu. Povarov ◽  
A. Mannig ◽  
G. Perren ◽  
J. S. Möller ◽  
E. Wulf ◽  
...  
Keyword(s):  
Spin System ◽  
Three Dimensional ◽  
Quantum Criticality ◽  
Zero Field

Charge-transfer driven ferromagnetism in a disordered three-dimensional 3d-5d spin system

2021 ◽  
pp. 168330
Author(s):  
Supratik Dasgupta ◽  
Philipp Komissinskiy ◽  
Pavan Nukala ◽  
Iliya Radulov ◽  
Andrei Rogalev ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Spin System ◽  
Three Dimensional

scholarly journals Towards ferromagnetic quantum criticality inFeGa3−xGex:Ga71NQR as a zero-field microscopic probe

2016 ◽  
Vol 93 (6) ◽  
Author(s):  
M. Majumder ◽  
M. Wagner-Reetz ◽  
R. Cardoso-Gil ◽  
P. Gille ◽  
F. Steglich ◽  
...  
Keyword(s):  
Quantum Criticality ◽  
Zero Field ◽  
Microscopic Probe

scholarly journals THREE-DIMENSIONAL GONIHEDRIC SPIN SYSTEM

2002 ◽  
Vol 17 (12) ◽  
pp. 751-761 ◽  
Author(s):  
G. KOUTSOUMBAS ◽  
G. K. SAVVIDY
Keyword(s):  
Phase Transition ◽  
Spin System ◽  
Order Approximation ◽  
Three Dimensional ◽  
Extrinsic Curvature ◽  
Original Model ◽  
Coupling Constants ◽  
Spin Interaction ◽  
First Order ◽  
Isotropic Point

We perform Monte–Carlo simulations of a three-dimensional spin system with a Hamiltonian which contains only four-spin interaction term. This system describes random surfaces with extrinsic curvature – gonihedric action. We study the anisotropic model when the coupling constants βS for the space-like plaquettes and βT for the transverse-like plaquettes are different. In the two limits βS = 0 and βT = 0 the system has been solved exactly and the main interest is to see what happens when we move away from these points towards the isotropic point, where we recover the original model. We find that the phase transition is of first order for βT = βS ≈ 0.25, while away from this point it becomes weaker and eventually turns to a crossover. The conclusion which can be drawn from this result is that the exact solution at the point βS = 0 in terms of 2D-Ising model should be considered as a good zero-order approximation in the description of the system also at the isotropic point βS = βT and clearly confirms the earlier findings that at the isotropic point the original model shows a first-order phase transition.

scholarly journals Effect of Anisotropy on the Critical Behaviour of Three- Dimensional Heisenberg Ferromagnets

1976 ◽  
Vol 31 (1) ◽  
pp. 34-40 ◽  
Author(s):  
R. Shanker ◽  
R. A. Singh
Keyword(s):  
Three Dimensional ◽  
Experimental Investigations ◽  
Isotropic Case ◽  
Zero Field ◽  
Critical Temperatures ◽  
Cubic Lattice ◽  
Simple Cubic ◽  
Simple Cubic Lattice ◽  
Anisotropic System ◽  
Critical Temperature Tc

The anisotropic nearest-neighbour Heisenberg model for the simple cubic lattice has been investigated by interpolating the anisotropy between the Ising and isotropic Heisenberg limits via general spin high-temperature series expansions of the zero-field suspectibility. This is done by estimating the critical temperature (Tc(3)) and the susceptibility exponent γ from the analysis of the series by the Ratio and Pade approximants methods. It is noted that Tc(3) varies with anisotropy while γ is almost the same for the anisotropic system, and a jump in it occurs for the isotropic case in agreement with the universality hypothesis. The effect of anisotropy on the susceptibility is also shown. Further, it is seen that estimates of γ for the two extreme limits agree well with those of previous theoretical as well as experimental investigations. In addition, critical temperatures have been summarised in a relation, and expressions for the magnetisation have been derived.

Magnetic Properties of the Random Mixture of the Classical Heisenberg Spins

1975 ◽  
Vol 53 (9) ◽  
pp. 854-860 ◽  
Author(s):  
Shigetoshi Katsura
Keyword(s):  
Critical Temperature ◽  
Nearest Neighbor ◽  
Linear Chain ◽  
Three Dimensional ◽  
Bethe Lattice ◽  
Zero Field ◽  
Qualitative Properties ◽  
Neighbor Interaction ◽  
Random Mixture ◽  
Ising Spins

The specific heat, the susceptibility, and the correlation function at zero field above the critical temperature of the random mixture (quenched site and bond problems) of the classical Heisenberg spins with nearest neighbor interaction were obtained exactly for the linear chain and for an infinite Bethe lattice (Bethe approximation of the two and three dimensional lattices) above the critical temperature. The results are simply expressed by the replacements of 2 cosh K → 4π (sinh K)/K and tanh K → L(K) (L(K) = Langevin function) for K = KAA, KAB, KBA, and KBB in the corresponding expressions of the random mixture of the Ising spins, and qualitative properties of both models are similar.

The gonihedric paradigm extension of the Ising model

2015 ◽  
Vol 29 (32) ◽  
pp. 1550203 ◽  
Author(s):  
George Savvidy
Keyword(s):  
Ising Model ◽  
Spin System ◽  
Three Dimensional ◽  
Spin Systems ◽  
Three Dimensions ◽  
Partition Functions ◽  
Random Surfaces ◽  
Four Dimensions ◽  
Vacuum States ◽  
Binary Information

In this paper we review a recently suggested generalization of the Feynman path integral to an integral over random surfaces. The proposed action is proportional to the linear size of the random surfaces and is called gonihedric. The convergence and the properties of the partition function are analyzed. The model can also be formulated as a spin system with identical partition functions. The spin system represents a generalization of the Ising model with ferromagnetic, antiferromagnetic and quartic interactions. Higher symmetry of the model allows to construct dual spin systems in three and four dimensions. In three dimensions the transfer matrix describes the propagation of closed loops and we found its exact spectrum. It is a unique exact solution of the three-dimensional statistical spin system. In three and four dimensions, the system exhibits the second-order phase transitions. The gonihedric spin systems have exponentially degenerated vacuum states separated by the potential barriers and can be used as a storage of binary information.

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