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Studies were made of the 1-70 keV persistent spectra of fifteen magnetars asa complete sample observed with Suzaku from 2006 to 2013. Combined with earlyNuSTAR observations of four hard X-ray emitters, nine objects showed a hardpower-law emission dominating at $\gtrsim$10 keV with the 15--60 keV flux of$\sim$1-$11\times 10^{-11}$ ergs s$^{-1}$ cm$^{-2}$. The hard X-ray luminosity$L_{\rm h}$, relative to that of a soft-thermal surface radiation $L_{\rm s}$,tends to become higher toward younger and strongly magnetized objects. Updatedfrom the previous study, their hardness ratio, defined as $\xi=L_{\rm h}/L_{\rms}$, is correlated with the measured spin-down rate $\dot{P}$ as $\xi=0.62\times (\dot{P}/10^{-11}\,{\rm s}\,{\rm s}^{-1})^{0.72}$, corresponding withpositive and negative correlations of the dipole field strength $B_{\rm d}$($\xi \propto B_{\rm d}^{1.41}$) and the characteristic age $\tau_{\rm c}$($\xi \propto \tau_{\rm c}^{-0.68}$), respectively. Among our sample, fivetransients were observed during X-ray outbursts, and the results are comparedwith their long-term 1-10 keV flux decays monitored with Swift/XRT andRXTE/PCA. Fading curves of three bright outbursts are approximated by anempirical formula used in the seismology, showing a $\sim$10-40 d plateauphase. Transients show the maximum luminosities of $L_{\rm s}$$\sim$$10^{35}$erg s$^{-1}$, which is comparable to those of the persistently bright ones, andfade back to $\lesssim$$10^{32}$ erg s$^{-1}$. Spectral properties arediscussed in a framework of the magnetar hypothesis.

Magnetar Broadband X-ray Spectra Correlated with Magnetic Fields: Suzaku Archive of SGRs and AXPs Combined with NuSTAR, Swift, and RXTE