Title: Berezinskii-Kosterlitz-Thouless Type Scenario in Molecular Spin Liquid $A$Cr$_2$O$_4$,
Abstract: The spin relaxation in chromium spinel oxides $A$Cr$_{2}$O$_{4}$ ($A=$ Mg,
Zn, Cd) is investigated in the paramagnetic regime by electron spin resonance
(ESR). The temperature dependence of the ESR linewidth indicates an
unconventional spin-relaxation behavior, similar to spin-spin relaxation in the
two-dimensional (2D) chromium-oxide triangular lattice antiferromagnets. The
data can be described in terms of a generalized Berezinskii-Kosterlitz-Thouless
(BKT) type scenario for 2D systems with additional internal symmetries. Based
on the characteristic exponents obtained from the evaluation of the ESR
linewidth, short-range order with a hidden internal symmetry is suggested.