Electronically competing phases and their magnetic field dependence in electrondoped nonsuperconducting and superconducting Pr0.88LaCe0.12CuO4-d
Pengcheng Dai
Department of Physics and Astronomy
The University of Tennessee
Knoxville, Tennessee 37996-1200, USA
Condensed Matter Sciences Division,
Oak Ridge National Laboratory
Oak Ridge, Tennessee 37831-6393, USA
We present comprehensive neutron scattering studies of nonsuperconducting and
superconducting electron-doped Pr0.88LaCe0.12CuO4-d (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) spindensity-wave (SDW) order is also induced, and both coexist with the residual threedimensional (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.