867 research outputs found
Magnetic Phase Transitions in the double spin-chains compound
We report high-resolution x-ray diffraction, muon-spin-rotation spectroscopic
and specific heat measurements in the double spin-chains compound . The x-ray diffraction results show that the crystal structure of
~is orthorhombic down to T=10K. Anisotropic line-broadening of
the diffraction peaks is observed, indicating disorder along the spin chains.
Muon spin relaxation and specific heat measurements show that
\~undergoes a phase transition to a magnetic ordered state at .
The specific heat data exhibits a second -like peak at , which increases with increasing magnetic field similarly way to
that found in spin-ladder compounds.Comment: 6 pages, 6 fifures, to appear in Physica
Ferro-type order of magneto-electric quadrupoles as an order-parameter for the pseudo-gap phase of a cuprate superconductor
Understanding the pseudo-gap phase from which a superconducting state emerges
is a central problem in the physics of cuprates. The phase exists below a
temperature T* for less than optimal doping of holes, and no clear jump in the
specific heat or change in lattice symmetry is observed on crossing T*. Here we
show that, two sets of intriguing experimental results in the literature
concerning magnetic properties of underdoped YBCO are united in a single theory
based on Cu quadrupole moments. The quadrupole is a product of spin and the
electric dipole, so there is no magnetic dipole moment, and standard
crystallography describes the magnetic motif. One experiment employed the Kerr
effect and the second Bragg diffraction of polarized neutrons, and both are
shown to imply an order-parameter for the pseudo-gap phase composed of
magneto-electric quadrupoles at in-plane Cu sites in a ferro-type order.
The successful interpretation of neutron diffraction data for YBCO yields the
first experimental evidence that neutrons are deflected by magneto-electric
multipoles. Predicted in 2014, our verification of the effect validates a new
application for the experimental technique of choice in studies of magnetic
motifs and excitations
Role of magnetic and orbital ordering at the metal-insulator transition in NdNiO3
Soft x-ray resonant scattering at the Ni L2,3 edges is used to test models of
magnetic and orbital-ordering below the metal-insulator transition in NdNiO3.
The large branching ratio of the L3 to L2 intensities of the (1/2,0,1/2)
reflection and the observed azimuthal angle and polarization dependence
originates from a non collinear magnetic structure. The absence of an orbital
signal and the non collinear magnetic structure show that the nickelates are
materials for which orbital ordering is absent at the metal-insulator
transition.Comment: 10 pages, 4 figures, Physical Review B rapid communication, to be
publishe
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