Tuning of superdiamagnetism in La2CuO4 by solid-state electrochemical fluorination and defluorination

Here, we demonstrate the electrochemical fluorination of La2CuO4 in an all-solid-state cell. This method of fluorine intercalation is controllable and reproducible, offering a precise adjustment of hole doping and thus tuning of superdiamagnetic (i.e., the perfect diamagnetic behavior of a superconductor) properties. The fluorinated La2CuO4Fx samples showed an increase in Tc and in diamagnetic response with increasing fluorine content with x up to ∼0.2. The fluorination process could also be reversed, as fluorine could be electrochemically deintercalated from La2CuO4Fx under re-formation of the antiferromagnetic insulator La2CuO4, returning the samples to a non-superdiamagnetic state. This method offers a convenient way of studying the detailed effects of hole doping in La2CuO4 and shows that tuning of material properties by electrochemical fluorination can also be extended to the field of superconductors.