Magnetic susceptibility and magnetization of the ionic ferromagnets dipotassium, dirubidium, and dicaesium tetrachlorochromate(II)

Abstract

High-temperature (300–80 K) susceptibility data are reported for polycrystalline samples of the ionic ferromagnets M₂CrCl₄(M = K, Rb, or Cs) and interpreted using the high-temperature series-expansion method for the quadratic-layer Heisenberg S= 2 ferromagnet to yield estimates of 7·0, 8·5, and 6·5 cm^–1 for the nearest-neighbour exchange integrals. Low-temperature (80–4·2 K) magnetization measurements are also reported for polycrystalline Rb₂CrCl₄ and Cs₂CrCl₄. In both compounds the magnetization obeys the equation {1 –[M(T)/M(0)]}=CT^γ with γ= 1·54 up to 60 K, i.e. ca 0·9 T_c. Saturation magnetizations are ca 0·4 B.M. lower than expected for S= 2 ions.