?
Competition between dynamic and structural disorder in a doped triangular fntiferromagnet RbFe(MoO4)2
Magnetisation measurements and ESR spectra of a doped quasi 2D antiferromagnet on a triangular lattice reveal a crucial change of the ground state spin configuration and a disappearance of a characteristic 1/3-magnetisation plateau under a doping.
According to theory, this is a result of the competition between the structural and dynamic disorders.
The dynamic zero-point or thermal fluctuations are known to lift the degeneracy of the mean field ground state of a triangular magnet and cause the spin configuration to be the most collinear, while the static disorder provides another selection of the ground state, with the least collinear structure.
Low-level doping was found to decrease the N\'{e}el temperature and saturation field by only few percent, while the magnetisation plateau disappears completely and the spin configuration is drastically changed.
ESR spectra confirm an impurity-induced change of the so-called Y-type structure to an inverted Y-structure for 15%-doping by potassium.