  Based on the magnetization, an accretion disk with large-scale magnetic field
can be separated into either standard and normal evolution (SANE) or
magnetically arrested disk (MAD), which are difficult to identify from
observations. It is still unclear whether all the radio-loud active galactic
nuclei (RLAGNs) with a thin disk and strong radio emissions contain a MAD. We
investigate this issue by utilizing the 3CRR catalog. We compile a sample of 35
quasars and 14 high-excitation radio galaxies powered by a thin accretion disk.
In order to consistently compare with the MAD sample given by Li et al. (2022),
the optical-UV emissions of our sample are all detected by the Hubble Space
Telescope (HST). It is found that the average X-ray luminosity ($L_{\rm X}$) of
our sample is about 5.0 times higher than that of radio-quiet AGNs (RQAGNs)
with matching optical-UV luminosity ($L_{\rm UV}$), in general accord with the
factor of 4.5 times in MAD sample within the uncertainty. The relationship
between radio (5~GHz) and X-ray (2 keV) luminosities in the 3CRR sources is
also found to be consistent with the MAD sample. Furthermore, the jet
efficiencies of 3CRR sources are consistent with those from the GRMHD
simulations of MAD. Therefore, we suggest that probably all the quasars and at
least a fraction of high-excitation radio galaxies in the 3CRR catalog, and
perhaps all the RLAGNs with strong radio emissions contain a MAD.
