烧结Sr_(1-x)Ca_xRuO_3系列的结构与磁性

STRUCTURE AND MAGNETIC PROPERTIES OF SINTERED Sr1-xCaxRuO3 SERIES

固相反应法制备了Sr1-xCaxRuO3系列,X射线衍射确定样品的相结构为正交畸变钙钛矿结构.随Ca替代量x的增加,晶格常数a基本保持不变,而b和c随之减小,晶格畸变更加明显.物理性质测量系统（PPMS）测量了样品的交流磁化率,零场冷却和加场冷却磁化强度.Curie-Weiss定律确定了样品的顺磁Curie温度Tp.结果表明,随x的增加,Tp减小.当x<0.6时Tp大于零;当x>0.6时Tp小于零.利用交流磁化率随温度变化的关系确定样品的铁磁Curie温度Tc,随x的增加Tc减小.当x=0.8时,Tc降至4K;而当x=1.0时,即使温度降到1.7K,也未出现磁有序.样品磁性随Ca替代量x的变化是其结构变化的直接结果.

Sr1-xCaxRuO3 series was prepaxed by a solid state reaction method and characterized by X-ray diffraction, which showed that the structure is orthorhombically distorted perovskite with space group of Pbnm. The lattice parameter a keeps almost constant with the Ca content x increasing, but the lattice parameters b and c decrease with x increasing. The orthorhombical distortion becomes larger with more substitution of calcium. The paramagnetic Curie temperature T-P was obtained by Curie-Weiss law, and T-P decreases with x increasing. When x less than or equal to0.6, T-P is positive, but when x >0.6, T-P is negative. The ferromagnetic Curie temperature T-C was obtained by the peak of susceptibility against temperature, and T-C decreases with x increasing. When x=0.8, T-C is down to 4 K. When x=1.0, no magnetic ordered phase was observed even though the temperature is down to 1.7 K. The differences in magnetic properties between SrRuO3 and CaRuO3 are due to their crystalline structures.