Temperature dependence of emission lifetimes in the site-diluted quasi-two-dimensional antiferromagnets (RNH3)2MnxCd1–xCl4(R = CH3 or C2H5)

Abstract

The temperature dependence of the emission from the ⁴T_1g state of the quasi-two-dimensional antiferromagnetic salts (RNH₃)₂MnCl₄(R = CH₃ or C₂H₅) and of solid solutions in which the Mn²⁺ is substituted by Cd²⁺ have been measured from 4 to 300 K. Discontinuities in the variation of the longest-lifetime component τ with temperature do not result from variations in energy-transfer rates caused by spin-spin correlations, as claimed by previous authors, since they become progressively more accentuated as the concentration of Cd²⁺ increases. Neither do they correlate with known structural phase-transition temperatures. The non-monotonic temperature dependence of τ is ascribed to splitting of the single ion ⁴T_1g by lower-symmetry ligand-field and spin-orbit coupling.