We have studied the effect of Co doping on the magnetic properties of multiferroic Mn 1−x Co x WO 4 using vibrating sample magnetometry and neutron powder diffraction. We find that Co doping at x տ 0.05 suppresses the commensurate AF1 phase and stabilizes the incommensurate spiral AF2 phase down to the lowest temperature. As the Co doping concentration increases further, a spin-flop transition occurs with the spiral-basal plane tilting off the b axis. Such magnetic structure expects a ferroelectric polarization component along the a axis. The resulting phase diagram is richer than the case of Fe doping.

The guest dynamics and thermal behavior occurring in the cages of clathrate hydrates appear to be too complex to be clearly understood through various structural and spectroscopic approaches, even for the well-known structures of sI, sII, and sH. Neutron diffraction studies have recently been carried out to clarify the special role of guests in expanding the host water lattices and have contributed to revealing the influence factors on thermal expansivity. Through this letter we attempt to address three noteworthy features occurring in guest inclusion: (1) the effect of guest dimension on host water lattice expansion; (2) the effect of thermal history on host water lattice expansion; and (3) the effect of coherent/incoherent scattering cross sections on guest thermal patterns. The diatomic guests of H 2, D 2, N 2, and O 2 have been selected for study, and their size and mass dependence on the degree of lattice expansion have been examined, and four sII clathrate hydrates with tetrahydrofuran (THF) have been synthesized in order to determine their neutron powder diffraction patterns. After thermal cycling, the THF + H 2 clathrate hydrate is observed to exhibit an irreversible plastic deformation-like pattern, implying that the expanded lattices fail to recover the original state by contraction. The host-water cage dimension after degassing the guest molecules remains as it was expanded, and thus host-guest as well as guest-guest interactions will be altered if guest uptake reoccurs.

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Solid solutions of xBiFeO3–yPrFeO3–zPbTiO3 (x+y+z=1) and (1−w)BiFeO3–wPbTiO3 have been explored for finding ferroelectromagnetic bulk material, in which ferroelectricity and ferromagnetism coexist simultaneously. The coexistence has been observed only in some ternary composition samples, that is, 0.2BiFeO3–0.2PrFeO3–0.6PbTiO3 and 0.4BiFeO3–0.2PrFeO3–0.4PbTiO3. In the ternary solid solutions, spontaneous magnetic moments disappear with the decrease of PrFeO3 content to y<0.2 independently of BiFeO3 content. When PrFeO3 content remains constant at y=0.2, the ternary solid solutions become paraelectric with the decrease of PbTiO3 content to z⩽0.2. The ferroelectromagnetic solid solutions have the noncentrosymmetric and doubled perovskite unit cell with a space group I4cm (a=b≈5.4 Å, c≈7.9 Å). Addition of Ta2O5 dopant substantially changes the polarization–electric-field and magnetization–magnetic field curves of the 0.2BiFeO3–0.2PrFeO3–0.6PbTiO3. The binary solid solutions of (1−w)BiFeO3–wPbTiO3 do not exhibit spontaneous magnetic moments down to 10 K over the entire composition range.

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