  We present comprehensive neutron scattering studies of nonsuperconducting and
superconducting electron-doped Pr0.88LaCe0.12CuO4(PLCCO). At zero field, the
transition from antiferromagnetic (AF) as-grown PLCCO to superconductivity
without static antiferromagnetism can be achieved by annealing the sample in
pure Ar at different temperatures, which also induces an epitaxial
(Pr,La,Ce)2O3 phase as an impurity. When the superconductivity first appears in
PLCCO, a quasi-two-dimensional (2D) spin-density-wave (SDW) order is also
induced, and both coexist with the residual three-dimensional (3D) AF state. A
magnetic field applied along the [-1,1,0] direction parallel to the CuO2 plane
induces a ``spin-flop'' transition, where the noncollinear AF spin structure of
PLCCO is transformed into a collinear one. The spin-flop transition is
continuous in semiconducting PLCCO, but gradually becomes sharp with increasing
doping and the appearance of superconductivity. A c-axis aligned magnetic field
that suppresses the superconductivity also enhances the quasi-2D SDW order at
(0.5,0.5,0) for underdoped PLCCO. However, there is no effect on the 3D AF
order in either superconducting or nonsuperconducting samples. Since the same
field along the [-1,1,0] direction in the CuO2 plane has no (or little) effect
on the superconductivity, (0.5,0.5,0) and (Pr,La,Ce)2O3 impurity positions, we
conclude that the c-axis field-induced effect is intrinsic to PLCCO and arises
from the suppression of superconductivity.
