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We measured the temperature dependences of the static magnetization and the spin excitation in the square-lattice multiferroic Ba_{2}MnGe_{2}O_{7}. An anisotropy gap of the observed low-energy mode is scaled by electric polarization rather than a power of the sublattice moment. Spin-nematic interaction in the effective spin Hamiltonian, which is equivalent to interaction of the electric polarization, is responsible for the easy-axis anisotropy. The nontrivial behavior of the anisotropy gap can be rationalized as change in the hybridized d-p orbital with temperature, leading to the temperature dependence of the spin-nematic interaction.

We present a neutron scattering study of the chromate spinel LiInCr4O8, which realizes a "breathing" pyrochlore lattice of S = 3/2 spins. High-resolution neutron diffraction reveals a phase separation into a mixture of minority cubic and majority tetragonal phases below 18 K, followed by apparent magnetic order in a complex two-up two-down pattern in the latter around 12 K. The spin-spin correlation length appears to remain small down to 1.7 K. Above both transitions, time-of-flight neutron spectroscopy shows that the response is inelastic rather than quasielastic, consistent with the relatively large alternation in sizes of adjacent Cr tetrahedra. Finally, a remarkable softening of the inelastic mode is observed preceding the structural transition, implying proximity to a critical point. [ABSTRACT FROM AUTHOR]

A spin-singlet ground state with a spin gap has been discovered in antiferromagnetic spin chain substances when the spin value is 1/2, 1, or 2. To find spin-gap (singlet-triplet) excitations in spin-3/2 chain substances, we performed inelastic neutron scattering and magnetization measurements on RCrGeO5 (R = Y or Sm) powders. As expected, we observed spin-gap excitations and the dispersion relation of the lowest magnetic excitations. We proved that the spin system of Cr3+ was an antiferromagnetic alternating spin-3/2 chain. We describe the influence of frustration between nearest-neighbor and next-nearest-neighbor exchange interactions in the chain. [ABSTRACT FROM AUTHOR]

We investigate the magnetic order of the buckled honeycomb lattice antiferromagnet Ba2NiTeO6 and its related antiferromagnet Ba3NiTa2O9 by neutron diffraction measurements. We observe magnetic Bragg peaks below the transition temperatures, and identify propagation vectors for these oxides. A combination of representation analysis and Rietveld refinement leads to a collinear magnetic order for Ba2NiTeO6 and a 120° structure for Ba3NiTa2O9. We find that the spin model of the bilayer triangular lattice is equivalent to that of the twodimensional buckled honeycomb lattice having magnetic frustration. We discuss the magnetic interactions and single-ion anisotropy of Ni2+ ions for Ba2NiTeO6 in order to clarify the origin of the collinear magnetic structures. Our calculation suggests that the collinear magnetic order of Ba2NiTeO6 is induced by the magnetic frustration and easy-axis anisotropy. [ABSTRACT FROM AUTHOR]

Investigating exotic magnetic materials with spintronic techniques is effective at advancing magnetism as well as spintronics. In this work, we report unusual field-induced suppression of the spin Seebeck effect (SSE) in a quasi-one-dimensional frustrated spin-1/2 magnet LiCuVO4, known to exhibit spin-nematic correlation in a wide range of external magnetic field B. The suppression takes place above |B|≳2 T in spite of the B-linear isothermal magnetization curves in the same B range. The result can be attributed to the growth of the spin-nematic correlation while increasing B. The correlation stabilizes magnon pairs carrying spin 2, thereby suppressing the interfacial spin injection of SSE by preventing the spin-1 exchange between single magnons and conduction electrons at the interface. This interpretation is supported by integrating thermodynamic measurements and theoretical analysis on the SSE. [ABSTRACT FROM AUTHOR]

We use inelastic neutron scattering to study the low-energy spin excitations of the 112-type iron pnictide Ca0.82 La0.18 Fe0.96 Ni0.04 As2 with bulk superconductivity below Tc = 22 K. A two-dimensional spin resonance mode is found around E = 11 meV, where the resonance energy is almost temperature independent and linearly scales with Tc along with other iron-based superconductors. Polarized neutron analysis reveals the resonance is nearly isotropic in spin space without any L modulations. Because of the unique monoclinic structure with additional zigzag arsenic chains, the As 4p orbitals contribute to a three-dimensional hole pocket around the Γ point and an extra electron pocket at the X point. Our results suggest that the energy and momentum distribution of the spin resonance does not directly respond to the kz dependence of the fermiology, and the spin resonance intrinsically is a spin-1 mode from singlet-triplet excitations of the Cooper pairs in the case of weak spin-orbital coupling. [ABSTRACT FROM AUTHOR]

We carried out inelastic neutron scattering experiments on a buckled honeycomb lattice antiferromagnet Ba2NiTeO6 exhibiting a stripe structure at a low temperature. Magnetic excitations are observed in the energy range of ℏω≲10 meV having an anisotropy gap of 2 meV at 2 K. We perform spin-wave calculations to identify the spin model. The obtained microscopic parameters are consistent with the location of the stripe structure in the classical phase diagram. Furthermore, the Weiss temperature independently estimated from a bulk magnetic susceptibility is consistent with the microscopic parameters. The results reveal that a competition between the nearest-neighbor and next-nearest-neighbor interactions that together with a relatively large single-ion magnetic anisotropy stabilize the stripe magnetic structure. [ABSTRACT FROM AUTHOR]

Ba2CoGe2O7 exhibits a collinear-antiferromagnetic structure with the easy axis along 〈100〉 directions and an antiferroelectric order with the polarization axis along the [001] direction. By applying the electric field the magnetic moment rotates from 〈100〉 to [110] directions and, simultaneously, the antiferroelectric state changes to the ferroelectric state gradually. This magnetoelectric effect, i.e., continuous control of the local magnetic moment by the electric field, is quantitatively explained by the Hamiltonian including the dielectric energy. [ABSTRACT FROM AUTHOR]