  Studies were made of the 1-70 keV persistent spectra of fifteen magnetars as
a complete sample observed with Suzaku from 2006 to 2013. Combined with early
NuSTAR observations of four hard X-ray emitters, nine objects showed a hard
power-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. Updated
from the previous study, their hardness ratio, defined as $\xi=L_{\rm h}/L_{\rm
s}$, 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 with
positive 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, five
transients were observed during X-ray outbursts, and the results are compared
with their long-term 1-10 keV flux decays monitored with Swift/XRT and
RXTE/PCA. Fading curves of three bright outbursts are approximated by an
empirical formula used in the seismology, showing a $\sim$10-40 d plateau
phase. 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, and
fade back to $\lesssim$$10^{32}$ erg s$^{-1}$. Spectral properties are
discussed in a framework of the magnetar hypothesis.
