Ordering Process and Its Hole Concentration Dependence of the Stripe Order in La{2-x}Sr{x}NiO{4}

Ordering process of stripe order in La{2-x}Sr{x}NiO{4} with x being around 1/3 was investigated by neutron diffraction experiments. When the stripe order is formed at high temperature, incommensurability \epsilon of the stripe order has a tendency to show the value close to 1/3 for the samples with x at both sides of 1/3. With decreasing temperature, however, \epsilon becomes close to the value determined by the linear relation of \epsilon = n_h, where n_h is a hole concentration. This variation of the \epsilon strongly affects the character of the stripe order through the change of the carrier densities in stripes and antiferromagnetic domains.Comment: 5 pages, 3 figures, REVTeX, to be published in Phys. Rev.

Specific heat study of spin-structural change in pyrochlore Nd2_2Mo2_2O7_7

By measurements of specific heat, we have investigated the magnetic field ($H$) induced spin-structural change in Nd$_2$Mo$_2$O$_7$ that shows spin-chirality-related magneto-transport phenomena. A broad peak around 2 K caused by the ordering of 2-in 2-out structure of the Nd moments at zero $H$ shifts to the lower temperature ($T$) up to around 3 T and then to the higher $T$ above around 3 T with increasing $H$ for all the direction of $H$. This is due to the crossover from antiferromagnetic to ferromagnetic arrangement between the Nd and Mo moments. While the peak $T$ increases monotonically above 3 T for $H$//[100], another peak emerges around 0.9 K at 12 T for $H$//[111], which is ascribed to the ordering of 3-in 1-out structure. For $H$//[110], a spike like peak is observed at around 3 T, which is caused perhaps by some spin flip transition.Comment: 5 pages, 4 figure

Electric Control of Spin Helicity in a Magnetic Ferroelectric

Magnetic ferroelectrics or multiferroics, which are currently extensively explored, may provide a good arena to realize a novel magnetoelectric function. Here we demonstrate the genuine electric control of the spiral magnetic structure in one of such magnetic ferroelectrics, TbMnO3. A spin-polarized neutron scattering experiment clearly shows that the spin helicity, clockwise or counter-clockwise, is controlled by the direction of spontaneous polarization and hence by the polarity of the small cooling electric field.Comment: 4 pages, 3 figure