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Johnson R.D.,University of Oxford | Johnson R.D.,Rutherford Appleton Laboratory | Cao K.,University of Oxford | Chapon L.C.,Laue Langevin Institute | And 7 more authors.
Physical Review Letters | Year: 2013

Structural and magnetic chiralities are found to coexist in a small group of materials in which they produce intriguing phenomenologies such as the recently discovered Skyrmion phases. Here, we describe a previously unknown manifestation of this interplay in MnSb2O6, a trigonal oxide with a chiral crystal structure. Unlike all other known cases, the MnSb2O6 magnetic structure is based on corotating cycloids rather than helices. The coupling to the structural chirality is provided by a magnetic axial vector, related to the so-called vector chirality. We show that this unique arrangement is the magnetic ground state of the symmetric-exchange Hamiltonian, based on ab initio theoretical calculations of the Heisenberg exchange interactions, and is stabilized by out-of-plane anisotropy. MnSb 2O6 is predicted to be multiferroic with a unique ferroelectric switching mechanism. © 2013 American Physical Society.

Kim H.S.,Korea Basic Science Institute | Kim H.S.,Pohang University of Science and Technology | Kim T.-H.,Pohang University of Science and Technology | Yang J.,Pohang University of Science and Technology | And 4 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2014

We investigate atomic and electronic structures of the intriguing low-temperature phase of IrTe2 using high-resolution scanning tunneling microscopy and spectroscopy. We confirm various stripe superstructures such as ×3, ×5, and ×8. The strong vertical and lateral distortions of the lattice for the stripe structures are observed in agreement with recent calculations. The spatial modulations of electronic density of states are clearly identified as separated from the structural distortions. These structural and spectroscopic characteristics are not consistent with the charge-density wave and soliton lattice model proposed recently. Instead, we show that the Ir (Te) dimerization together with the Ir 5d charge ordering can explain these superstructures, supporting the Ir dimerization mechanism of the phase transition. © 2014 American Physical Society.

Mun E.,Los Alamos National Laboratory | Mun E.,Simon Frazer University | Weickert F.,Los Alamos National Laboratory | Kim J.,Los Alamos National Laboratory | And 8 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2016

We investigate partially disordered antiferromagnetism in CoCl2-2SC(NH2)2, in which ab-plane hexagonal layers are staggered along the c axis rather than stacked. A robust 1/3 state forms in applied magnetic fields in which the spins are locked, varying as a function of neither temperature nor field. By contrast, in zero field and applied fields at higher temperatures, partial antiferromagnetic order occurs, in which free spins are available to create a Curie-like magnetic susceptibility. We report measurements of the crystallographic structure and the specific heat, magnetization, and electric polarization down to T=50mK and up to μ0H=60T. The Co2+S=3/2 spins are Ising-like and form distorted hexagonal layers. The Ising energy scale is well separated from the magnetic exchange, and both energy scales are accessible to the measurements, allowing us to cleanly parametrize them. In transverse fields, a quantum Ising phase transition can be observed at 2 T. Finally, we find that magnetic exchange striction induces changes in the electric polarization up to 3μC/m2, and single-ion magnetic anisotropy effects induce a much larger electric polarization change of 300μC/m2. © 2016 American Physical Society.

Eom M.J.,Pohang University of Science and Technology | Kim K.,Pohang University of Science and Technology | Jo Y.J.,Kyungpook National University | Yang J.J.,Pohang University of Science and Technology | And 6 more authors.
Physical Review Letters | Year: 2014

We report a de Haas-van Alphen (dHvA) oscillation study on IrTe2 single crystals showing complex dimer formations. By comparing the angle dependence of dHvA oscillations with band structure calculations, we show distinct Fermi surface reconstruction induced by a 1=5-type and a 1=8-type dimerizations. This verifies that an intriguing quasi-two-dimensional conducting plane across the layers is induced by dimerization in both cases. A phase transition to the 1=8 phase with higher dimer density reveals that local instabilities associated with intra- and interdimer couplings are the main driving force for complex dimer formations in IrTe2. © 2014 American Physical Society.

Hearmon A.J.,University of Oxford | Hearmon A.J.,Diamond Light Source | Johnson R.D.,University of Oxford | Johnson R.D.,Rutherford Appleton Laboratory | And 7 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2013

The hexaferrites are known to exhibit a wide range of magnetic structures, some of which are connected to important technological applications and display magnetoelectric properties. We present data on the low magnetic field structures stabilized in a Y-type hexaferrite as observed by resonant soft x-ray diffraction. The helical spin block arrangement that is present in zero applied magnetic field becomes fanlike as a field is applied in plane. The propagation vectors associated with each fan structure are studied as a function of magnetic field, and a new magnetic phase is reported. Mean field calculations indicate this phase should stabilize close to the boundary of the previously reported phases. © 2013 American Physical Society.

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