Incommensurate-Commensurate Magnetic Phase Transitions of the Ising-5f System UPd_2Si_2 : the H-T Phase Diagram and Mean-Field Analyses

概要

論文の詳細を見る
The naagnetic, transport, and thermal properties have been sttrdied irr UPdzSi3 single crystalsby variotrs experiments inclttding netrtron diffraction and ultra-high-field (H< 1 MOe) naagne-tization. The entire featture of H -T magnetic pl?ase diagram has been obtained, for the firsttiraue. Three distinct ordered phases are observed, xvith a strong trniaxial anisotropy along thetetragonal c-axis. One of the notable feattrres revealed in the ordered phases is 21 f'ormationof an incotnzaaensurate-longitudinal-sine-wave (ICLSW) tnodtrl?ttion in the tenaperature range108 K< T< 135 K, where the propagation vector Q ('vO.TIc" at 135 K) varies contintrotrslyas a function of ternperattrre, with no admixttrre of' hartnonics. The taaagnetic susceptibility exhibits an tznusual f'erroraaagnetic enhancernent in this antif'errotnagnetically ordered st?tte. Theentropy analyses using 21 non-5 f analog ThPdxSin have confirtned that the anomalotus unagneticproperties of UPdzSiz are ascribed to the 5 f tnouaaents of uranitrm ions, which are replaceablewith Ising pseudo-spins. A phenornenological strgtnrnent has been detnonstrated on the basis ofthe axiarl-next-nearest-neighbor Ising (ANNNI) model within a tnean-field approxinaa,Lion. Thecalcttlatiotas with a finite-size approxitnation reproduce the observed magnetic phase diagrazaasurprisingly well.
社団法人日本物理学会の論文
1998-03-15