相关论文: Two Ferromagnetic Phases in Spin-Fermion Systems

We investigate the low-temperature behavior of ferromagnets with a spontaneously broken symmetry O(3) $\to$ O(2). The analysis is performed within the perspective of nonrelativistic effective Lagrangians, where the dynamics of the system is…

We introduce a novel approach for the investigation of spin-wave excitations in itinerant ferromagnets. Our theory is based on a variational treatment of general multi-band Hubbard models which describe elements and compounds of transition…

We use bosonization to derive the effective field theory that properly describes ferromagnetic transition in one-dimensional itinerant electron systems. The resultant theory is shown to have dynamical exponent z=2 at tree leve and upper…

The weak ferromagnet FeBO$_3$ is well known for being a unique system for modelling and testing magnetic dynamics primarily due to relatively simple and localized magnetic structure and its interesting spin wave dynamics. At room…

A broad continuum-like spin excitation (1--10 meV) with a peak structure around 2.4 meV has been observed in the ferroelectric $ab$ spiral spin phase of Gd$_{0.7}$Tb$_{0.3}$MnO$_3$ by using terahertz (THz) time-domain spectroscopy. Based on…

The magnetic phase diagram of the ferromagnetic Kondo lattice model is determined at T=0 in 1D, 2D, and 3D for various magnitudes of the quantum mechanical localized spins ranging from S=1/2 to classical spins. We consider the ferromagnetic…

Spin-polarons are obtained using an Ising-like exchange model consisting of double and super-exchange interactions in low dimensional systems. At zero temperature, a new phase separation between small magnetic polarons, one conduction…

Topological phase space disconnection has been recently found to be a general phenomenon in isolated anisotropic spin systems. It sets a general framework to understand the emergence of ferromagnetism in finite magnetic systems starting…

We introduce an alternative thermal diffusive dynamics for the spin-S Ising ferromagnet realized by means of a random walker. The latter hops across the sites of the lattice and flips the relevant spins according to a probability depending…

By mapping the hamiltonian of the spin one ferromagnet onto that of the classical spherical model we investigate the possible phase transitions and the phase diagram of the spin one ferromagnet. Similarly to what happens in the spherical…

An isotropic half-metallic double exchange magnet with a direct superexchange coupling between the localized spins is studied within the spin-wave (1/S) expansion. The momentum dependence of the spin wave spectrum (including quantum…

We perform magnetic susceptibility and magnetic torque measurements on the organic $\kappa$-(BEDT-TTF)$_2$Hg(SCN)$_2$Br, which is recently suggested to host an exotic quantum dipole-liquid in its low-temperature insulating phase. Below the…

Electronic excitations in a ferromagnet can trigger ultrafast spin dynamics with potential applications in a speed increase in magnetic recording. The project investigates ultrafast magnetization dynamics, which is driven in metallic layers…

The magnetization evolution of the free layer in an orthogonal spin-torque device is studied based on a macrospin model. The trajectory of magnetization vector under various conditions has shown rich nonlinear properties. The phase diagram…

The thermodynamic properties of ferromagnetic spin chains have been analyzed with a variety of microscopic methods over the years: Bethe ansatz, spin-wave theory, Schwinger-boson mean-field theory, Green functions and renormalization group…

In this study the magnetic order of the spin-1/2 XXZ chain system Cs$_2$CoCl$_4$ in a temperature range from 50 mK to 0.5 K and in applied magnetic fields up to 3.5 T is investigated by high-resolution measurements of the thermal expansion…

The spherical spin model with infinite-range ferromagnetic interactions is investigated analytically in the framework of non-extensive thermostatics generalizing the Boltzmann-Gibbs statistical mechanics. We show that for repulsive…

We have implemented three approaches to describe the thermodynamic properties of ferrimagnetic ($S=5/2, s=2$) spin chains. The application of cumulant expansion has been generalized to the ferrimagnetic chain in the presence of an external…

Using an extended Lee-Yang theorem and GKS correlation inequalities, we prove, for a class of ferromagnetic multi-spin interactions, that they will have a phase transition(and spontaneous magnetization) if, and only if, the external field…

Low temperature properties of antiferromagnetic two-leg spin-1/2 ladders with bond randomness and site dilution (or doping with nonmagnetic impurities) are studied using the real-space renormalization-group technique. We find that for non…