We have detected an error in our data retrieval script which prepares the measured transmission data for the conversion to magnetic permeability. Correcting this error requires modification of Fig. 4(b) and Fig. 5 in the original publication. All methods, calculations and the conclusion in the published paper are still correct.
© 2014 Optical Society of America
Due to an error in the data retrieval script, the imported magnitude of the transmission data used for calculating the magnetic permeability was not correct. This leads to a mistake in the results obtained for μ r,eff. In section 4 of the paper , Fig. 4(b) and Fig. 5 have to be replaced by Fig. 1 and Fig. 2 below.
Both, Fig. 1 and 2 show, that the magnetic permeability varies between −0.1 and 3. It should be emphasized, that a measurement on the same sample at lower temperature (T = 2.3K) did show a stronger negative permeability due to an increased quality factor of the SQUID resonance. This result is presented in Fig 3. The lowest value of the real part of μ r,eff reached in this measurment is Re(mur,eff) = −1.