Observation of magnetic dimers in the diluted triangular-lattice spin liquid candidate NaYbO2

The triangular-lattice spin liquid (QSL) candidate NaYbO2 is magnetically diluted by Lu doping, forming homogeneous solid solutions NaYb1-xLuxO2 (0 <= x<1.0). A combination of structural, magnetic, and pulsed high-field electron spin resonance analysis shows that the lattice parameters and the Curie-Weiss temperature theta(CW) vary almost linearly with x, and the crystal electric field environment of the Yb/Lu ions persists during the Lu doping. The statistical distribution analysis of clusters and the deduced linear theta(CW) similar to x relation indicate that the nearest neighbor exchange J does not change with magnetic dilution. Interestingly, with the magnetization measurement at 0.39 K, we have observed S-eff = 1/2 antiferromagnetic Yb-Yb dimers in NaYb0.02Lu0.98O2, which is manifested as a magnetization step at mu H-0(c) = 2.68 T due to the transition between singlet and triplet states. Thus, the intradimer interaction is directly determined as J/k(B) = -5.15 K. Surprisingly, this value is close to the interaction of undoped NaYbO2, supporting the theoretical analysis of clusters. Our study provides a method of estimating the magnetic interaction of QSL materials through magnetic dilution. The statistical distribution analysis of magnetic clusters suggests that through a small amount of Lu doping (x < 0.5), the QSL state in NaYbO2 can continue to be maintained.