A-type antiferromagnetic order, 2D ferromagnetic fluctuation and orbital order in stoichiometric La1-xEuxMnO3

• Main Authors: Chin-Tao Chen, 陳錦濤
• Other Authors: Huan-Chiu Ku
• Format: Others
• Language: en_US
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/07648583266876252085

碩士 === 國立清華大學 === 物理學系 === 90 === Structural, magnetic and Mn K-edge X-ray absorption structure (XANES) spectrum studies for the La1-xEuxMnO3+d system and other rare earth manganite compounds are reported. The maximum formula unit volume Vf.u., appearance of A-type antiferromagnetic (AF) order with Néel temperature TN ranging from 139 K for LaMnO3 to 42 K for EuMnO3, and the two-dimensional (2D) ferromagnetic short-range fluctuation with T2D > TN in low field is the direct result of anisotropic superexchange interaction for the A-type AF order with strong basal plane ferromagnetic coupling of the orbital-ordered eg electrons (with orbital ordering temperature TOO > room temperature) and weak c-axis antiferromagnetic coupling of t2g electrons. The anomalous decreasing of T2D and TN with increasing Eu parameter x is due to more localized t2g electrons from stronger crystal field splitting and lattice distortion. Both T2D and TN are field dependent and nearly merges at higher applied field.