Predictions of thermomagnetic properties of Laves phase compounds: TbAl_2, GdAl_2 and SmAl_2 performed with ATOMIC MATTERS MFA computation system

摘要

Recent calculations of properties of TbAl2 GdAl2 and SmAl2 single crystals, performed with our new computation system called ATOMIC MATTERS MFA are presented. We applied localized electron approach to describe the thermal evolution of Fine Electronic Structure of Tb3+, Gd3+ and Sm3+ ions over a wide temperature range and estimate Magnetocaloric Effect (MCE). Thermomagnetic properties of TbAl2, GdAl2 and SmAl2 were calculated based on the fine electronic structure of the 4f(8), 4f(7) and 4f(5) electronic configuration of the Tb3+ and Gd3+ and Sm3+ ions, respectively. Our calculations yielded: magnetic moment value and direction; single-crystalline magnetization curves in zero field and in external magnetic field applied in various directions m(T,B-ext); the 4f-electronic components of specific heat c(4f)(T,B-ext); and temperature dependence of the magnetic entropy and isothermal entropy change with external magnetic field - Delta S(T, B-ext). The cubic universal CEF parameters values used for all CEF calculations was taken from literature and recalculated for universal cubic parameters set for the RAl2 series: A(4) = +7.164 Ka(0)(4) and A(6) = -1.038 Ka(0)(6). Magnetic properties were found to be anisotropic due to cubic Laves phase C15 crystal structure symmetry. These studies reveal the importance of multipolar charge interactions when describing thermomagnetic properties of real 4f electronic systems and the effectiveness of an applied self-consistent molecular field in calculations for magnetic phase transition simulation. (C) 2017 Elsevier B.V. All rights reserved.