In this article we apply a recently invented analytical real-space renormalization group formulation which is based on numerical concepts of the density matrix renormalization group. Within a rigorous mathematical framework we construct non-perturbative renormalization group transformations for the spin1 2 XXX Heisenberg model in the finite temperature regime. The developed renormalization grou...

We develop the theory of exchange/dipole spin wave excitations of ferromagnetic nanowires of cylindrical cross section, where the magnetization is parallel to the axis of the wire. In addition, we provide the theory of the microwave response of such structures, for the case where the nanowire is also a conductor. We present explicit calculations of both the mode structure of nanowires, and also...

The natural explanation of the excitation spectrum of the spin1 antiferromagnetic Heisenberg chain is given from the viewpoint of the spin-1/2 ferromagnetic-antiferromagnetic alternating Heisenberg chain. The energy spectrum of the latter is calculated with fixed momentum k by numerical diagonalization of finite size systems. It consists of a branch of propagating triplet pair (triplet wave) an...

Spin and charge fluctuations and superconductivity in Na0.35CoO2·1.3H2O are studied based on a multi-orbital Hubbard model. By applying the fluctuation exchange (FLEX) approximation, we show that the Hund’s-rule coupling between the Co t2g orbitals causes ferromagnetic spin fluctuation. Triplet pairing is favored by this ferromagnetic fluctuation on the hole-pocket band. We propose that, in Na0...

The magnetic properties of the ferromagnetic Kondo-lattice model (FKLM) are investigated. Starting from an analysis of the magnon spectrum in the spin-wave regime, we examine the ferromagnetic stability as a function of the occupation of the conduction band n and the strength J of the coupling between the localised moments and the conduction electrons. From the properties of the spin-wave stiff...

Using ground state computations, we study the transition from a spin glass to a ferromagnet in 3D spin glasses when changing the mean value of the spin-spin interaction. We find good evidence for replica symmetry breaking up until the critical value where ferromagnetic ordering sets in, and no ferromagnetic spin glass phase. This phase diagram is in conflict with the droplet/scaling and mean fi...

X-ray photoemission electron microscopy is used to probe the remnant magnetic domain structure in high quality, single-crystalline, exchange-biased Fe/MnPd bilayers. It is found that the induced unidirectional anisotropy strongly affects the overall magnetic domain structure. Real space images of the ferromagnetic domains provide direct evidence for an asymmetric magnetization reversal process ...

We present a study of the ordering temperature of an ultrathin antiferromagnetic film in the proximity of a ferromagnetic layer. The Néel temperature of a single-crystalline antiferromagnetic FexMn1-x film on Cu(001) in contact with a ferromagnetic Ni layer was monitored by the discontinuity in the coercivity as a function of temperature by magneto-optical Kerr effect measurements. It decreases...