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The present work focuses on the effect of vanadium dioxide (VO2) films exhibiting a metal–insulator transition (MIT) on the performance characteristics of the magnetic multilayers. It has been shown that the MIT provides a novel mechanism for controlling the microwave spin-wave dynamics in the yttrium iron garnet (YIG) films. In particular, the low and high levels of microwave attenuation of spin waves transmitted through the YIG–VO2 bilayer has been observed due to a variation of the VO2 conductivity within a narrow temperature range. This effect has been utilized to realize fully reconfigurable magnonic crystals composed of the thickness-modulated YIG and regular VO2 films. A promising functionality of the proposed waveguiding structures arises from a controllability of wave intensity, which provides an altering of the frequency response from an original band structure to a full rejection of spin waves. Numerical simulations taking into account both the YIG film saturation magnetization and the VO2 film conductivity have confirmed the experimentally observed spin-wave dynamics. An interest in ferrite–VO2 bilayers arises not only from possible practical applications but also from a variety of fundamental scientific problems devoted to the physics of wave phenomena in planar thin-film magnetic multilayers. [ABSTRACT FROM AUTHOR]

We consider two cobalt-based full-Heusler compounds, CoFeTiAl and Co 2 FeSi, for which Coulomb correlation effects play an important role. Since the standard GGA scheme does not provide a precise description of the electronic properties near the Fermi level, we use a meta-GGA functional capable to improve the description of the electronic properties of CoFeTiAl and Co 2 FeSi. In particular, we find a better agreement with the experiment for the magnetic moment and the energy bandgap. Moreover, our calculations show that pressure enhances the insulating properties of Co 2 FeSi and CoTiFeAl. [ABSTRACT FROM AUTHOR]

A theory has been developed for the waveguiding characteristics of dual-tunable multiferroic magnonic crystals (MCs). The crystals are constructed as periodically width-modulated microwave transmission slot-lines placed in between thin ferrite and ferroelectric films. Dispersion characteristics of the spin-electromagnetic waves (SEWs) in the investigated periodic waveguiding structure were derived using the method of approximate boundary conditions and the coupled-mode approach. The transmission-loss characteristics (TLCs) were calculated by the transfer-matrix method. The results show that the TLCs of the structures consist of pass-bands and stop-bands. The stop-bands are due to Bragg reflections in the structure. The magnetic and electric fields control the stop-band frequencies. The ferroelectric film polarization produced with the application of control voltage to the slot-line electrodes reduces its dielectric permittivity and provides up-shift of the stop-band frequencies. The most effective electric tuning is achieved in the area of the maximum hybridization of SEWs. As a result, the investigated multiferroic MCs combine the advantages of thin-film planar topology and dual tunability of magnonic band-gaps. [ABSTRACT FROM AUTHOR]