Related papers: Order parameters in the Verwey phase transition
We present a theoretical analysis of the temperature-magnetic field-concentration phase diagram of the multiferroic Mn$_{1-x}$M$_{x}$WO$_{4}$ (M=Fe, Zn, Mg), which exhibits three ordered phases, with collinear and non-collinear…
The crystal structure of Fe3O4 below the 122 K Verwey transition has been refined using high-resolution X-ray and neutron powder diffraction data. The refinements give direct evidence for charge ordering (CO) over four independent…
We report on simulations of layered superconductors using the Lawrence-Doniach model in the framework of the lowest Landau level approximation. We find a first order phase transition with a $B(T)$ dependence which agrees very well with the…
A new mechanism of the Verway transition in magnetite (Fe3O4), which has been argued to be a charge ordering transition so far, is proposed. Based on the mean field calculations for the three band model of spinless fermions appropriate for…
We incorporate single crystal Fe$_3$O$_4$ thin films into a gated device structure and demonstrate the ability to control the Verwey transition with static electric fields. The Verwey transition temperature ($T_V$) increases for both…
We report the magnetic, thermal, magnetocaloric and transport properties of polycrystalline NdCuSi. The compound shows a weak antiferromagnetic ordering, as confirmed by different measurements. Arrott plots indicate that the magnetic phase…
In the present paper we generalised a phenomenological model developed in \cite{gomo:2005} for the description of magnetostructural phase transitions and related peculiarities of elastic properties in solid oxygen under high pressure and/or…
The magnetic response and fluxoid transitions of superconducting aluminum rings of various sizes, deposited under conditions likely to generate a layered structure, show good agreement with a two-order-parameter Ginzburg-Landau model. For…
Using low-energy electron diffraction, we show that the room-temperature $(\sqrt{2}\times\sqrt{2})R45^\circ$ reconstruction of Fe$_3$O$_4$(100) reversibly disorders at $\sim$450 $^\circ$C. Short-range order persists above the transition,…
We have studied the electronic structure and charge ordering (Verwey) transition of magnetite (Fe3O4) by soft x-ray photoemission. Due to the enhanced probing depth and the use of different surface preparations we are able to distinguish…
The dynamics of weak vs. strong first order phase transitions is investigated numerically for 2+1 dimensional scalar field models. It is argued that the change from a weak to a strong transition is itself a (second order) phase transition,…
We present a tunnel spectroscopy study of the electronic spectrum of single magnetite \chemform{Fe_3O_4} nanoparticles trapped between nanometer-spaced electrodes. The Verwey transition is clearly identified in the current…
The Verwey transition in magnetite (Fe$_3$O$_4$) is the first metal-insulator transition ever observed and involves a concomitant structural rearrangement and charge-orbital ordering. Due to the complex interplay of these intertwined…
We develop a generalized Ginzburg-Landau theory for second harmonic generation (SHG) in magnets by expanding the free energy in terms of the order parameter in the magnetic phase and the susceptibility tensor in the corresponding…
Exploiting Landau's theory of phase transformations, defining an original order parameter and using the phenomenological transformation temperatures, it is reported that it is possible to describe in a global approach the conditions for the…
The continuous phase transition, indicated by the macroscopic order parameter and the occurrence of the spontaneous symmetry breaking, is well illustrated based on the Ginzburg-Landau's paradigm. In systems described by one order parameter,…
At ambient conditions, the Fe$_3$O$_4$(001) surface shows a $(\sqrt{2}\times \sqrt{2})R45^o$ reconstruction that has been proposed as the surface analog of the bulk phase below the Verwey transition temperature, T$_V$. The reconstruction…
The thermodynamic model of visco-elastic deformable magnetic materials at finite strains is formulated in a fully Eulerian way in rates. The Landau theory applies for ferro-to-para-magnetic phase transition, the gradient theory (leading…
We develop a variational mean-field theory of the ferromagnetic transition in compounds like Lanthanum-Manganite within the framework of the Double-Exchange Model supplemented by modest disorder. We obtain analytical expressions for the…
Landau theory is used to investigate the behaviour of a metallic magnet driven towards a quantum critical point by the application of pressure. The observed dependence of the transition temperature with pressure is used to show that the…