22 research outputs found
Multiferroic behavior in the new double-perovskite LuMnCoO
We present a new member of the multiferroic oxides, LuMnCoO, which we
have investigated using X-ray diffraction, neutron diffraction, specific heat,
magnetization, electric polarization, and dielectric constant measurements.
This material possesses an electric polarization strongly coupled to a net
magnetization below 35 K, despite the antiferromagnetic ordering of the Mn and Co spins in an configuration along the c-direction. We discuss the magnetic order
in terms of a condensation of domain boundaries between and
ferromagnetic domains, with each domain boundary
producing a net electric polarization due to spatial inversion symmetry
breaking. In an applied magnetic field the domain boundaries slide, controlling
the size of the net magnetization, electric polarization, and magnetoelectric
coupling
Spiral spin-liquid and the emergence of a vortex-like state in MnScS
Spirals and helices are common motifs of long-range order in magnetic solids,
and they may also be organized into more complex emergent structures such as
magnetic skyrmions and vortices. A new type of spiral state, the spiral
spin-liquid, in which spins fluctuate collectively as spirals, has recently
been predicted to exist. Here, using neutron scattering techniques, we
experimentally prove the existence of a spiral spin-liquid in MnScS by
directly observing the 'spiral surface' - a continuous surface of spiral
propagation vectors in reciprocal space. We elucidate the multi-step ordering
behavior of the spiral spin-liquid, and discover a vortex-like triple-q phase
on application of a magnetic field. Our results prove the effectiveness of the
- Hamiltonian on the diamond lattice as a model for the spiral
spin-liquid state in MnScS, and also demonstrate a new way to realize a
magnetic vortex lattice.Comment: 10 pages, 11 figure
Magnetic Frustration Driven by Itinerancy in Spinel CoV2O4
Localized spins and itinerant electrons rarely coexist in geometrically-frustrated spinel lattices. They exhibit a complex interplay between localized spins and itinerant electrons. In this paper, we study the origin of the unusual spin structure of the spinel CoV2O4, which stands at the crossover from insulating to itinerant behavior using the first principle calculation and neutron diffraction measurement. In contrast to the expected paramagnetism, localized spins supported by enhanced exchange couplings are frustrated by the effects of delocalized electrons. This frustration produces a non-collinear spin state even without orbital orderings and may be responsible for macroscopic spin-glass behavior. Competing phases can be uncovered by external perturbations such as pressure or magnetic field, which enhances the frustration