40 research outputs found
NMR studies of the incommensurate helical antiferromagnet EuCo2P2 : determination of the antiferromagnetic propagation vector
Recently Ding et al. [Phys. Rev. B 95, 184404 (2017)] reported that their
nuclear magnetic resonance (NMR) study on EuCoAs successfully
characterized the antiferromagnetic (AFM) propagation vector of the
incommensurate helix AFM state, showing that NMR is a unique tool for
determination of the spin structures in incommensurate helical AFMs. Motivated
by this work, we have carried out Eu, P and Co NMR
measurements on the helical antiferromagnet EuCoP with an AFM ordering
temperature = 66.5 K. An incommensurate helical AFM structure was
clearly confirmed by Eu and P NMR spectra on single crystalline
EuCoP in zero magnetic field at 1.6 K and its external magnetic field
dependence. Furthermore, based on Co NMR data in both the paramagnetic
and the incommensurate AFM states, we have determined the model-independent
value of the AFM propagation vector k = (0, 0, 0.73 0.09)2/ where
is the -axis lattice parameter. The temperature dependence of k is also
discussed.Comment: 8 pages, 10 figures, accepted for publication in Phys. Rev. B. arXiv
admin note: substantial text overlap with arXiv:1704.0629
Physical properties of a new cuprate superconductor Pr_2Ba_4Cu_7O_{15-\delta}
We present studies of the thermal, magnetic and electrical transport
properties of reduced polycrystalline Pr_2Ba_4Cu_7O_{15-\delta} (Pr247) showing
a superconducting transition at Tc = 10 - 16 K and compare them with those of
as-sintered non-superconducting Pr247. The electrical resistivity in the normal
state exhibited T2 dependence up to approximately 150 K. A clear specific heat
anomaly was observed at Tc for Pr247 reduced in a vacuum for 24 hrs, proving
the bulk nature of the superconducting state. By the reduction treatment, the
magnetic ordering temperature TN of Pr moments decreased from 16 to 11 K, and
the entropy associated with the ordering increased, while the effective
paramagnetic moments obtained from the DC magnetic susceptibility varied from
2.72 to 3.13 mB. The sign of Hall coefficient changed from positive to negative
with decreasing temperature in the normal state of a superconducting Pr247,
while that of as-sintered one was positive down to 5 K. The electrical
resistivity under high magnetic fields was found to exhibit T^a dependence (a =
0.08 - 0.4) at low temperatures. A possibility of superconductivity in the
so-called CuO double chains is discussed.Comment: Science and Technology of Advanced Materials (in press
Helicity Selection of the Cycloidal Order in Noncentrosymmetric EuIrGe
The magnetic helicities of the cycloidal ordering in EuIrGe, with a
noncentrosymmetric tetragonal structure, have been studied by circularly
polarized resonant X-ray diffraction. It is shown that the helicity of each
cycloidal domain is uniquely determined and satisfies the symmetry relations of
the point group of the crystal structure. The result shows that the
cycloidal helicity is determined by the Dzyaloshinskii-Moriya type
antisymmetric exchange interaction. The domain selection and the phase
transition by the external magnetic field along [100] and [110] have also been
studied. It is shown that the cycloidal plane prefers to be perpendicular to
the field and the transverse conical state is realized.Comment: 6 pages, 4 figures, 5 figures in the supplemental material, accepted
for publication in J. Phys. Soc. Jp