Magnetic susceptibility and optical spectra of the organic-intercalated two-dimensional ferromagnets bis(monomethylammonium)- and bis(monoethylammonium) tetrachlorochromate(II)

Abstract

The title compounds have been prepared and characterised by chemical analysis and X-ray diffraction. By magmetic-susceptibility and magnetisation measurements they are shown to order ferromagnetically at T_c= 58 ± 2 and 55 ± 2 K respectively. Up to ca. 0.7 T_c the magnetisation M(T) obeys the equation 1 –[M(T)/M(0)]=CT^γ where γ= 1.5 ± 0.1. The optical spectra of both compounds contain sharp absorption bands at 533 and 626 nm, assigned as quintet–triplet ligand-field transitions. Up to 0.9 T_c their intensities vary with temperature as T², as predicted for ‘hot’ exciton–magnon combination bands in a two-dimensional easy-plane ferromagnet.