  Newly born magnetars are promising sources for gravitational wave (GW)
detection due to their ultra-strong magnetic fields and high spin frequencies.
Within the scenario of a growing tilt angle between the star's spin and
magnetic axis, due to the effect of internal viscosity, we obtain improved
estimates of the stochastic gravitational wave backgrounds (SGWBs) from
magnetic deformation of newly born magnetars. We find that the GW background
spectra contributed by the magnetars with ultra-strong toroidal magnetic fields
of 10^{17} G could roughly be divided into four segments. Most notably, in
contrast to the background spectra calculated by assuming constant tilt angles
\chi=\pi/2, the background radiation above 1000 Hz are seriously suppressed.
However, the background radiation at the frequency band \sim100-1000 Hz are
moderately enhanced, depending on the strengths of the dipole magnetic fields.
We suggest that if all newly born magnetars indeed have toroidal magnetic
fields of 10^{17} G, the produced SGWBs should show sharp variations with the
observed frequency at several tens to about 100 hertz. If these features could
be observed through sophisticated detection of the SGWB using the proposed
Einstein Telescope, it will provide us a direct evidence of the tilt angle
evolutions and further some deep understandings about the properties of newly
born magnetars.
