  We have measured the spin-dependent transverse asymmetry, A_T', in
quasi-elastic inclusive electron scattering from polarized 3He with high
precision at Q^2 = 0.1 to 0.6 (GeV/c)^2. The neutron magnetic form factor, GMn,
was extracted at Q^2 = 0.1 and 0.2 (GeV/c)^2 using a non-relativistic Faddeev
calculation that includes both final-state interactions (FSI) and
meson-exchange currents (MEC). In addition, GMn was extracted at Q^2 = 0.3 to
0.6 (GeV/c)^2 using a Plane Wave Impulse Approximation calculation. The
accuracy of the modeling of FSI and MEC effects was tested and confirmed with a
precision measurement of the spin-dependent asymmetry in the breakup threshold
region of the 3He(pol)(e(pol),e') reaction. The total relative uncertainty of
the extracted GMn data is approximately 3%. Close agreement was found with
other recent high-precision GMn data in this Q^2 range.
