以X光散射研究La5/3Sr1/3NiO4條紋調制結構的對稱性

3d過渡金屬氧化物La2-xSrxNiO4(LSNO)與高溫超導體La2-xSrxCuO4(LSCO)有著相同的I4/mmm結構，並且在低溫下都有著電荷條紋(charge stripes)以及自旋條紋(spin stripes)結構，但是LSCO的電荷條紋使其成為超導體而LSNO的電荷條紋則是使其形成莫特絕緣體，並且由電導率量測發現當LSNO的Sr摻雜達x = 1/3時與其他比例摻雜有著明顯的變化，並且由X光散射發現電荷條紋隨著溫度升高其相變過程有著逆有序-無序的變化，由中子散射結果得知LSNO中隨著溫度升高自旋條紋由有序到無序的過程中存在著條紋液體相，並且當自旋為條紋液體相時會成為幫助電荷條紋排列的阻尼，從而導致X光散射觀察到逆有序無序的變化。針對La5/3Sr1/3NiO4的單晶樣品使用電性量測的電阻與溫度關係圖來判斷電荷條紋的相變溫度TCO，以及使用磁性量測判斷自旋條紋的相變溫度TSO，之後藉由X光散射變溫實驗對電荷條紋QCO = (4.66 0 3)沿著L方向掃描判斷電荷條紋調制發生逆有序-無序的相變溫度，並且針對相變前的長程有序的T~150 K、相變發生時的T~210 K、相變途中的T~220 K以及相變結束的T~230 K進行方位角實驗，可以得知在電荷條紋始終是維持著二重對稱，並無隨著與自旋條紋液體耦合而發生變化。

關鍵字

La5/3Sr1/3NiO4 ；條紋調制；電荷條紋；方位角

並列摘要

The 3d transition metal oxide, La2-xSrxNiO4(LSNO)is isostructural to high-TC superconductor La2-xSrxCuO4(LSCO), and they both have charge stripes and spin stripes at low temperature. The charge stipes of LSCO let LSCO to be a superconductor but the charge stripes of LSNO make LSNO a Mott insulator. And the conductivity measurement shows that when the Sr doping is x = 1/3 in LSNO, it conductivity is obvious difference with other doping ratio. And X-ray scattering shows the phase transition of the charge stripes is inverse order-disorder change as the temperature increases. In addition the existence of spin stripe-liquid phase in La5/3Sr1/3NiO4 is demonstrated through neutron scattering measurements. Spin stripe-liquid will become a damping to suppress the disorder of the charge stripes, it is the reason of inverse order-disorder for charge stripes. For the LSNO single crystal sample, use the resistivity measurement and magnetic measurement to determine the phase transition temperature of the charge stripes (TCO¬) and spin stripes (TSO). And after that, we use X-ray scattering as function temperature for charge stripes QCO = (4.66 0 3). The L-scan can show the transition temperature of inverse order-disorder. For the long range ordering temperature T~150 K, the phase transition begin T~210 K, during the phase transition T~220 K, and the end of the phase transition T~230 K, the x-ray azimuthal scattering shows charge stripes is always two-fold symmetry. It does not change with the coupling with the spin stripe-liquid.