High-temperature heat capacity of Bi2CuO4

The heat capacity of Bi₂CuO₄ has been measured over a wide temperature range. The thermodynamic functions of the solid oxide compound have been calculated using the experimental data.     

High-temperature heat capacity of La2CuO4

The heat capacity of La₂CuO₄ has been measured in the temperature range 400–950 K. The temperature dependence of the heat capacity has been found to exhibit an extremum at 526 K.     

High-temperature heat capacity of Sm2CuO4 and Ho2Cu2O5

The heat capacities of Sm₂CuO₄ and Ho₂Cu₂O₅ have been measured in the temperature ranges 329–839 and 359–751 K, respectively. The experimental data have been used to determine the thermodynamic properties of the oxide compounds.     

High-temperature heat capacity of CuGa2O4

Experimental data on the heat capacity of CuGa₂O₄ in the range 329–1050 K are presented. The values of the thermodynamic functions (enthalpy and entropy changes) are calculated from smoothed values of the heat capacity.     

High-temperature heat capacity of Dy2Cu2O5

Data on the heat capacity of Dy₂Cu₂O₅ in the temperature range 346–981 K have been obtained. The experimental data have been used for determining the thermodynamic properties of this oxide compound.     

High-temperature heat capacity of Y2Cu2O5

The temperature dependence of the molar heat capacity of Y₂Cu₂O₅ has been measured at 328–953 K. The thermodynamic functions of the oxide compound have been calculated from the experimental data.     

Mössbauer study of magnetic ordering in57Co-doped Eu2CuO4 and Gd2CuO4

Zeeman splitting of Mossbauer spectra of⁵⁷Co doped into Eu₂CuO₄ and Gd₂CuO₄ indicates magnetic ordering of Cu moments for temperatures below about 150 K in Eu₂CuO₄ and below about 200 K in Gd₂CuO₄. Supported by NASA Grant NAG 3-847     

High-temperature heat capacity of YFe3(BO3)4

The molar heat capacity of YFe₃(BO₃)₄ has been measured using differential scanning calorimetry in the temperature range 339–1086 K. It has been found that the dependence C _p = f(T) exhibits an extremum at a temperature of 401 K due to the structural transition.     

High-temperature heat capacity of TbFe3(BO3)4

The molar heat capacity of TbFe₃(BO₃)₄ in the temperature range of 346–1041 K has been measured by differential scanning calorimetry. It has been found that the C _p = f(T) curve does not show extremes. The thermodynamic properties of the oxide compound have been determined from the experimental data.     

Magnetoelectric effect and magnetic dynamics in the Gd2CuO4 antiferromagnet

The magnetoelectric effect and the magnetic dynamics in Gd₂CuO₄ have been studied using a phenomenological approach and group-theory methods. Vector order parameters are introduced based on four magnetic sublattices. Invariant products of the order parameters are determined, from which the thermodynamic potential density is constructed. Using the spin-wave representation, the calculations can be significantly simplified and the ground orientation magnetic state can be presumably determined. The magnetic dynamics is described by the Landau-Lifshitz equations, from which the antiferromagnetic resonance frequency and the dynamic susceptibilities, namely, magnetic, antiferromagnetic, magnetoelectric, and antiferroelectric susceptibilities are found. The frequency and the susceptibility are shown to be controlled by applied electric field.     

High-temperature heat capacity of the BiFeO3 multiferroic

Data on the heat capacity of the BiFeO₃ multiferroic have been obtained within a broad temperature interval. Correlation has been established between the composition of the Bi₂O₃-Fe₂O₃ pseudobinary system and the specific heat capacity of the oxide compounds.     

Effect of hydrogen doping on the magnetic properties of Gd2CuO4

We report the results of ac-susceptibility and dc-magnetization measurements for H_yGd₂CuO₄ (0y0.54). It is shown thatH doping lowers the weak ferromagnetic component in the material. The distinct hysteresis loops observed atT=77 K for both non- and hydrogenated samples change its shape withy. The magnetic ordering temperatures T _N ^Cu and T _N ^Gd , as determined from the temperature dependencies of ac-susceptibility, remain unchanged with sample's hydrogenation. This result seems to indicate that extra electrons are not doped onto the Cu-O planes of Gd₂CuO₄. The frequency dependencies ofx(, T) andx(, T) for bothy=0 andy=0.15 samples are analysed., The maximums ofx andx found at about 200K are considered in terms of susceptibility dependence on the spin-lattice relaxation time (). The anomalies in ac-susceptibility found recently in Gd₂CuO₄ atT _a=8 K andT _b=9.5 K decrease significantly withy. Results are discussed in the context of available data on 214T-type compounds.     

Magnon heat transport in doped La2CuO4

We present results of the thermal conductivity of La2CuO4 and La(1.8)Eu(0.2)CuO4 single crystals which represent model systems for the two-dimensional spin-1/2 Heisenberg antiferromagnet on a square lattice. We find large anisotropies of the thermal conductivity which are explained in terms of two-dimensional heat conduction by magnons within the CuO2 planes. Nonmagnetic Zn substituted for Cu gradually suppresses this magnon thermal conductivity kappa(mag). A semiclassical analysis of kappa(mag) is shown to yield a magnon mean free path which scales linearly with the reciprocal concentration of Zn ions.