Related papers: Spin-spiral states in undoped manganites
We study the ground state orbital ordering of $LaMnO_3$, at weak electron-phonon coupling, when the spin state is A-type antiferromagnet. We determine the orbital ordering by extending to our Jahn-Teller system a recently developed Peierls…
A double exchange model for degenerate $e_g$ orbitals with intra- and inter-orbital interactions has been studied for the electron doped manganites A$_{1-x}$B$_{x}$MnO$_3$ ($x > 0.5$). We show that such a model reproduces the observed phase…
The spin-spiral (SS) type of magnetization is studied with the Hubbard model. Consideration of noncollinearity of the magnetic moments results in a phase diagram which consists of regions of the SS and paramagnetic states depending on the…
We characterize the coexistence of itinerant ferromagnetism and spin-triplet superconductivity within a single mechanism involving local (Hund's rule) exchange among $d$ electrons. The ratio of transition temperatures and the spin…
Spin wave excitations were measured in the ferromagnetic phase of Nd$_{1/2}$Sr$_{1/2}$MnO$_{3}$ by neutron scattering. This compound is located in proximity to the A-type antiferromagnetic state, and it shows a clear anisotropy and…
We investigate the highly frustrated spin and orbital superexchange interactions in cubic vanadates. The fluctuations of $t_{2g}$ orbitals trigger a {\it novel mechanism of ferromagnetic interactions} between spins S=1 of V$^{3+}$ ions…
The spin-charge-orbital complex structures of manganites are studied using topological concepts. The key quantity is the "winding number" w associated with the Berry-phase connection of an e_g electron parallel-transported through…
The double exchange (DE) model is systematically applied for studying the coupling between ferroelectric (FE) and magnetic orders in several prototypical types of multiferroic manganites. The model was constructed for the magnetically…
This work examines the effects of magnetic frustration due to competing ferromagnetic and antiferromagnetic Heisenberg interactions on the spin dynamics of the double-exchange model. When the local moments are non-colinear, a charge-density…
We construct the 1/S spin-wave expansion for double exchange ferromagnets at T=0. It is assumed that the value of Hund's rule coupling, J_H, is sufficiently large, resulting in a fully saturated, ferromagnetic half-metallic ground state. We…
We discuss a mechanism of real-space spin-triplet pairing, alternative to that due to quantum paramagnon excitations, and demonstrate its applicability to $\mathrm{UGe_2}$. Both the Hund's rule ferromagnetic exchange and inter-electronic…
The origin of ferromagnetic insulating state of La$_{7/8}$Sr$_{1/8}$MnO$_3$ is investigated. Based on the tight-binding model, it is shown that this state can be attributed to the Peierls instability arisen from the interplay of spin and…
Exploring new magnetic materials is essential for finding advantageous functional properties such as magnetoresistance, magnetocaloric effect, spintronic functionality, and multiferroicity. Versatile classes of double perovskite compounds…
We explore a phenomenological phase diagram for the magnetic helical state with 90$^{\circ}$ turn angle between neighboring spins in the external magnetic field. Such state is formed by the Eu spin layers in the superconducting iron…
Through a combination of neutron diffraction and Landau theory we describe the spin ordering in the ground state of the quadruple perovskite manganite CaMn7O12 - a magnetic multiferroic supporting an incommensurate orbital density wave that…
By combining neutron four-circle diffraction and polarized neutron diffraction techniques we have determined the complex spin structures of a multiferroic, YMn2O5, that exhibits two ferroelectric phases at low temperatures. The obtained…
Magnetoelectric phase diagrams of the perovskite manganites, Eu1-xYxMnO3 and Gd1-xTbxMnO3, are theoretically studied. We first construct a microscopic model, and then analyze the model using the Monte-Carlo method. We reproduce the…
Spin-reorientation phase transitions that involve the rotation of a crystal$'$s magnetization have been well characterized in distorted-perovskite oxides such as the orthoferrites. In these systems spin reorientation occurs due to competing…
We have analyzed different correlation functions in a realistic spin-orbital model for half-doped manganites. Using a finite-temperature diagonalization technique the CE phase was found in the charge-ordered phase in the case of small…
Doped and undoped manganites are modeled by the coupling between itinerant $e_g$ electrons and static $t_{2g}$ spins, the Jahn-Teller and breathing phonon modes, and the Coulomb interaction. We provide for a careful estimate of all…