Ferromagnetic phase transition and anomalies of thermodynamic characteristics of copper-deficient EuCu2P2 at low temperaturesстатья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 30 сентября 2020 г.
Аннотация:A homogeneous powder sample of EuCu2P2 was synthesized from the elements by a two-step high temperature ampule technique. X-ray powder diffraction analysis have shown that the compound belongs to the ThCr2Si2 structure type and features copper deficiency. The study of temperature changes of heat capacity, Cp(T) (2e300 K), and unit cell parameters, a(T) and c(T) and volume Vu(T) (5e300 K), revealed a pronounced anomaly at about TСmах ¼ 44 K evidencing the phase transition to the ferromagnetic state. Detailed analyses of the extracted excess (magnetic) components of EuCu2P2 thermodynamic characteristics, Cm(T) and DVm(T), have been performed using the Debye-Einstein and mean field theory approaches. We have found that the anomalous nature of Cm(T) and DVm(T) at T < TС(mах) is caused by the effect of the internal magnetic field on the magnetic moments of Eu2þ ions, and, to a lesser extent, by the splitting of the ground state of Eu2þ ions. Noticeable anisotropy of the EuCu2P2 thermal expansion at temperatures below TCmax as well as a significant effect of the anharmonicity of lattice vibrations on the thermal properties of EuCu2P2 at elevated temperatures have been documented.