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We report on the temperature (T), magnetic field (μ0H), and angle (Θ, Φ) dependent resonant absorption of X-band microwaves in spinel ferrite epitaxial films subjected to two distinct states of growth strain. The polar angle (Θ) dependence of the resonance field (Hres) in films with ∼0.5% ab-plane expanded unit cell establishes a distinct perpendicular magnetic anisotropy (PMA). The anisotropy field (Han┴) for Θ = 0° increases monotonically on lowering the temperature from 300 K to 90 K following the behavior of the saturation magnetization (Ms) keeping Han┴/Ms ≈ 1. The narrow resonance linewidth (μ0ΔHres┴ = 3.7 mT at 300 K) and its negligible (±0.3 mT) variation with temperature establish the magnetic softness of these PMA films. The dependence of Hres on Θ, Φ, and T in films subjected to compressive stress shows in-plane cubic anisotropy whose strength is nonmonotonic in temperature. The ∼2.0% compression of the unit cell basal plane also appears to accentuate noncollinearity of sublattice magnetization of such films as indicated by the T-dependence of ΔHres. The thicker films with PMA display spin wave resonances whose position allows determination of the spin wave stiffness constant together with independent determination of Han┴. The resonance characteristics of the PMA films qualify them as potential candidates for frequency agile microwave devices and magnonic circuit elements. [ABSTRACT FROM AUTHOR]

A double-fluid theory is used to find the electromagnetic wave absorption of carbon monoxide with iron-catalyzed high-pressure disproportionation (HiPco)-grown single-walled carbon nanotubes (SWNTs). The electromagnetic wave absorption of carbon monoxide with HiPco SWNTs is obtained and is studied numerically. The absorption is then deduced and their functional dependence on the number density, collision frequency, cyclotron frequency, and angle of propagation is studied. The double-fluid theory predicts that there is an electromagnetic frequency dependency on the energy absorption properties of the system under investigation. The calculation results show that effects of magnetic field strength and the angle of microwave propagation on the absorption coefficient as well as the frequency band of resonant absorption are very significant. [ABSTRACT FROM AUTHOR]

The magnetic ordering of an easy-plane Van Vleck magnet with a large anisotropy of the easy-plane type and an antiferromagnetic exchange interaction between spins is considered in the case when the ground state of the integer-spin ions is a singlet and the antiferromagnetic phase is realized only in an external magnetic field. It is found that the phase transformation of the singlet (paramagnetic) phase to the antiferromagnetic phase is a quantum phase transition belonging to the magnetic phase transitions of the displacive type. It is shown that the Landau theory of phase transitions is applicable to such a transformation, with the order parameter being the polarization of the singlet state. Nonstandard manifestations of the paraprocess converting the second-order magnetic phase transition of the displacive type to a first-order transition are noted. The phase diagram is constructed; it differs from those of classical antiferromagnets in that the antiferromagnetic phase on it is surrounded only by the paramagnetic phase. [ABSTRACT FROM AUTHOR]