Related papers: Order parameters in the Verwey phase transition
The statement that any phase transition is related to the appearance or disappearance of long-range spatial correlations precludes a finite transition temperature in one-dimensional (1D) systems. In this paper we demonstrate that the 1D…
We derive a free energy for weakly anisotropic ferromagnets which is valid in the whole temperature range and interpolates between the micromagnetic energy at zero temperature and the Landau free energy near the Curie point T_c. This free…
Electronic structure calculations of the Verwey ground state of magnetite, Fe3O4, using density functional theory with treatment of on-site Coulomb interactions (DFT+U scheme) are reported. These calculations use the recently-published…
General conditions are formulated that allow to determine which quantum phase transitions in itinerant electron systems can be described by a local Landau-Ginzburg-Wilson or LGW theory solely in terms of the order parameter. A crucial…
We study a model system with nematic and magnetic orders, within a channel geometry modelled by an interval, $[-D, D]$. The system is characterised by a tensor-valued nematic order parameter $\mathbf{Q}$ and a vector-valued magnetisation…
We present the results of a comparative analysis of the magnetocaloric effect (MCE) in Pr0.7Sr0.2Ca0.1MnO3, through direct and indirect measurements, using experimentally measured magnetization, specific heat, magnetostriction, resistivity,…
The study of critical phenomena and phase transitions is an important part of modern condensed matter physics. In this regard, the phenomenological Landau theory has been extraordinarily useful. Hereby we present an alternative theoretical…
We discuss a framework relying on both perturbative and non-perturbative lattice computations which will be able to reliably determine the parameters of the EW phase transition. A motivation for the use of 3d effective theory in the lattice…
The complex conductivity at the (Verwey) metal-insulator transition in Fe_3O_4 has been investigated at THz and infrared frequencies. In the insulating state, both the dynamic conductivity and the dielectric constant reveal a power-law…
In a recent letter, J. P. Wright et al [Phys. Rev. Lett. 87,266401 (2001) and cond-mat/0111119] have investigated the crystal structure of magnetite below the Verwey transition temperature (TV) by means of X-ray and neutron powder…
It is well established that physical quantities like the heavy quark potentials get temperature independent at sufficiently short distances. As a first application of this feature we suggest a new order parameter for the…
With use of homogeneous model for magnetic sub-lattice of compound La1-x CaxMnO3 allowing for Heisenberg superexchange and double exchange between nearest neighbors the temperature dependence of spontaneous magnetization on a separate site…
For relaxor-ferroelectrics and relaxor-ferromagnets, Ehrenfest classification of phase transitions based on the discontinuity of entropy or specific heat etc. with temperature (T) gives no transition that contradicts the measured order…
Magnetic and structural properties of magnetite nanoparticles stabilized in polyvinyl-alcohol thin films are investigated by using X-ray diffraction (XRD), transmission electron microscopy (TEM), electron paramagnetic resonance (EPR) and…
This work investigates the magnetically driven ferroelectricity in orthorhombic manganites RMnO3 (R=Gd, Dy or Tb) from the point of view of the symmetry. The method adopted generalizes the one used to characterize the polar properties of…
The hydrodynamic theory of polar liquid crystals is widely used to describe biological active fluids as well as passive molecular materials. Depending on the `shear-alignment parameter', in passive or weakly active polar fluids under…
We present a lattice model to study the equilibrium phase diagram of ordered alloys with one magnetic component that exhibits a low temperature phase separation between paramagnetic and ferromagnetic phases. The model is constructed from…
We provide evidence for the existence of a {\em quantum critical point} at the metallization of magnetite Fe$_{3}$O$_{4}$ at an applied pressure of $p_{c} \approx 8$ GPa. We show that the present ac magnetic susceptibility data support…
We study the finite temperature phase diagram of the Heisenberg-Kitaev model on a three dimensional hyperhoneycomb lattice. Using semiclassical analysis and classical Monte-Carlo simulations, we investigate quantum and thermal…
Taking into account both the orbital and the paramagnetic depairing effects we derive a simple analytic formula for the temperature dependence of the Ginzburg-Landau parameter valid in vicinity of field dependent critical temperature in a…