Specific-heat-capacity measurements confirm a second-order magnetic phase transition with a substantial magnetic contribution that persists to low temperature. Here, the domain length along the c axis is substantially larger than the pitch length of 48 nm found for the helimagnetic state in C r 1 / 3 Nb S 2.

The expectation of a significant Dzyaloshinskii-Moriya interaction in this chiral-structured magnet, along with the helical state discovered in isostructural C r 1 / 3 Nb S 2, suggest either a long period helical state with q ~ 0.0025 Å - 1, or FM regions separated by magnetic solitons, may be responsible for the apparent small size of the FM domains. This indicates either a short-range ferromagnetic (FM) order with a domain size of ~250 nm along the c axis or a possible magnetic modulation with a large pitch length. Below T C, neutron diffraction reveals increased scattering near the structural Bragg peaks having a wider Q dependence along the c axis than the nuclear Bragg peaks. M n 1 / 3 Nb S 2 displays a magnetic transition at T C ~ 45 K with highly anisotropic behavior expected for a hexagonal-structured material. We more » have investigated here the structural, magnetic, thermodynamic, and charge-transport properties of M n 1 / 3 Nb S 2 single crystals through x-ray and neutron diffraction, magnetization, specific heat, magnetoresistance, and Hall-effect measurements. The temperature-dependent unit cell volume could be described well using the Debye approximation with a Debye temperature of Θ D ≃ 294 K, consistent with the heat capacity data. We have also demonstrated that 1 / T 1 31 in high temperatures varies linearly with 1 / H, reflecting the effect of spin diffusion on the dynamic susceptibility. Moreover, the NMR spin-lattice relaxation rates show the dominant contributions from uniform ( q = 0 ) and staggered ( q = ± π / a ) spin fluctuations in the high- and low-temperature regimes, respectively, mimicking one-dimensionality of the spin lattice. From the value of T N, the average interchain coupling is estimated to be J ' / k B ≃ 0.28 K. The diverging trend of NMR spin-lattice relaxation rates ( 1 / T 1 31 and 1 / T 1 23 ) implies the onset of a magnetic long-range ordering at around T N ≃ 1 K. The corresponding mapping using first-principles electronic structure calculations leads to J DFT / k B ≃ 59 K with negligibly small interchain couplings, further confirming that the system is indeed a one-dimensional uniform spin- 1 2 Heisenberg antiferromagnet. The temperature-dependent magnetic susceptibility and P 31 NMR shift could be modeled very well by the uniform spin- 1 2 Heisenberg antiferromagnetic chain model with a nearest-neighbor interaction J / k B ≃ 58.7 K.

Here we presen more » t the structural and magnetic properties of KNaCuP 2 O 7 investigated via x-ray diffraction, magnetization, specific heat, and P 31 and Na 23 NMR measurements and complementary electronic structure calculations. The Dzyaloshinskii-Moriya (DM) interaction is present in the transition metal dichalcogenides (TMDC) magnets of form M 1 / 3 T S 2 ( M = 3 d transition metal, T ϵ ,

Knoxville 2016 rfactor download