Novel zero-gap compounds, magnetics: CuFeS₂and CuFeTe₂

Abstract

The temperature dependences of the Hall coefficient R(T), specific conductivity sigma (T), and electron concentration n(T) of CuFeS2 and CuFeTe2 monocrystals are investigated. From their power dependences the zero bandgap for the electron excitations of these substances is established. Analysis of the temperature dependence of the mobility mu (T) enables the authors to conclude that the conduction electrons are in the magnetopolaron (ferron) state of large and small radius in CuFeS2 and CuFeTe2 respectively. The existence of various power dependences R(T), sigma (T) and n(T) in CuFexAl1-xS2 solid solutions, in the CuFeS2 compound, which is under pressure, and in the CuFeTe2 compound, is pointed out. These anomalies are explained both by the manifestation of peculiarities of the ferron spectrum and by various mechanisms of ferron mobility. It is pointed out that the theoretical group analysis of the CuFeS2 structure corroborates the possibility of the existence of the zero-gap state at the P point of the Brillouin zone. Some peculiarities of the zero-gap spectra of the both substances are discussed.