Direct observation of the ground state of a 1/3 quantum magnetization plateau in SrMn3_3P4_4O14_{14} using neutron diffraction measurements

We can directly investigate the ground state in magnetization-plateau fields (plateau ground state) using neutron diffraction measurements. We performed neutron diffraction measurements on the spin-5/2 trimer substance SrMn$_3$P$_4$O$_{14}$ in magnetization-plateau fields. The integrated intensities of magnetic reflections calculated using an expectation value of each spin in a plateau ground state of an isolated-trimer model agree well with those obtained experimentally in the magnetization-plateau fields. We succeeded in direct observation of a plateau ground state in SrMn$_3$P$_4$O$_{14}$

Spiral magnetic structure in spin-5/2 frustrated trimerized chains in SrMn3P4O14

We study a spin-5/2 antiferromagnetic trimerized chain substance SrMn3P4O14 using neutron powder diffraction experiments. The coplanar spiral magnetic structure appears below T_N1 = 2.2(1) K. Values of several magnetic structure parameters change rapidly at T_N2 = 1.75(5) K, indicating another phase transition, although the magnetic structures above and below T_N2 are the qualitatively same. The spiral magnetic structure can be explained by frustration between nearest-neighbor and next-nearest-neighbor exchange interactions in the trimerized chains.Comment: submitted to Phys. Rev.

Negative magnetization of Li2Ni2Mo3O12 having a spin system composed of distorted honeycomb lattices and linear chains

We study themagnetism of a spin-1 substance Li2Ni2Mo3O12. The spin system consists of distorted honeycomb lattices and linear chains of Ni2+ spins. Li+ ions enter about 25% and 50% of the honeycomb and chain Ni sites, respectively, creating disorder in both spin subsystems. A magnetic phase transition occurs at Tc = 8.0 K in the zero magnetic field. In low magnetic fields, the magnetization increases rapidly below Tc, decreases below 7 K, and finally becomes negative at low temperatures. We determine the magnetic structure using neutron powder diffraction results. The honeycomb lattices and linear chains show antiferromagnetic and ferromagnetic long-range order, respectively. We investigate static and dynamic magnetic properties using the local probe technique of muon spin relaxation. We discuss the origin of the negative magnetization

Temperature dependence of the pressure-induced amorphization of ice Ih studied by high-pressure neutron diffraction to 30 K

International audienceHigh-pressure neutron diffraction allowed the in situ observation of the pressure-induced amorphization of ordinary ice Ih between 130 and 30 K, i.e., to lower temperatures than any other diffraction study before. We find that the pressure required for complete transformation into high-density amorphous ice !HDA" increases with decreasing temperature to #80 K but remains approximately constant below. Our findings support earlier evidence of two distinct mechanisms responsible for the pressure-induced amorphization in ice Ih, namely, amorphization due to mechanical melting down to lowest temperatures, and amorphization due to thermal melting at elevated temperatures. Such scenario naturally explains why HDA prepared through compression at 77 K is structurally distinct from the form of HDA obtained by the compression of low-density amorphous ice !LDA" and hence cannot be associated with the hypothesized high-density proxy of liquid water in a two-state model

Synthesis, Structure, and Properties of New Perovskite PbVO₃

The new perovskite PbVO3 was synthesized under high-temperature and high-pressure conditions. Its crystal structure (a = 3.80005(6) Å, c = 4.6703(1) Å, Z = 1, S.G. P4mm) contains isolated layers of corner-shared VO5 pyramids, which are formed instead of octahedra due to a strong tetragonal distortion (c/a = 1.23). The lead atom is shifted out of the center of the unit cell toward one of two [VO2]-layers due to the influence of the lone pair. This new perovskite exhibits a semiconductor-like ρ(T) dependence down to 2 K. This behavior can be qualitatively explained by taking into account strong electron correlations in electronic structure calculations