Inverse order-disorder transition of charge stripes

We report an unusual transition behavior of charge stripes in La1.67Sr0.33NiO4 using x-ray scattering. The segregated holes in La1.67Sr0.33NiO4 are observed to form anisotropic stripes in the a × b plane of the crystal space below the transition temperature T 238 K, and at the same time, display an unusual inverse order-disorder transition along the c axis. Using a phenomenological Landau theory, we show that this inverse transition is due to the interlayer coupling between the charge and spin orders. This discovery points to the importance of the interlayer correlations in the strongly correlated electrons system.