ESR study of the Prussian blue analogue Rb0.8Mn1.1[Fe(CN)6]·D2O

Abstract We performed electron spin resonance (ESR) studies of the mixed valence Prussian blue analogue, Rb 0.8 Mn 1.1 [Fe(CN) 6 ]·D 2 O in a wide frequency (9.5–319 GHz) and temperature (3.5–300 K) interval. Evidence for the proposed high-temperature Mn 2+ ( S = 5 2 )–NC–Fe 3+ ( S = 1 2 ) to low-temperature Mn 3+ ( S =2)–NC–Fe 2+ ( S =0) internal charge transfer has been detected: a characteristic reduction of χ ESR T on cooling from room temperature to 100 K, a particular frequency dependence of the room temperature ESR linewidth, and the temperature dependence of the ESR linewidth. Short-range magnetic correlations, reflected in a large broadening and dramatic shift of the ESR signal develop just above T C =10 K. Below T C , both the linewidth and the shift in position mimic the temperature dependence of the order parameter. In a quench experiment T C was reduced by 3 K. The observed ferromagnetic ordering arises from Mn 3+ ( S =2) moments in the low-temperature electronic configuration.