Anisotropy in magnetic and transport properties of RT-antimonide(3) (R = lanthanum-samarium, gadolinium; T = chromium, vanadium).

摘要

RTSb₃ is an anisotropic, low dimensional system, with orthorhombic crystal structure. This work investigates RCrSb₃ which is an itinerant ferromagnet for R = La-Nd, and Sm, and a ferrimagnet for R = Gd. RVSb ₃ (R = La, Sm, and Gd) has also been investigated in order to compare the results with an isostructural, non-magnetic system. LaCrSb₃ has a rich phase diagram with a ferromagnetic transition at T _C = 132 K due to the Cr interactions. At low fields a high temperature antiferromagnetic transition is found at T_N = 98 K which is unique in the series to LaCrSb₃.; With the substitution of other light rare-earths, the Curie temperature is reduced, and a second low temperature magnetic ordering phase is observed due to the 4f-ions. SmCrSb₃ is unique in the system due to its strong first order antiferromagnetic transition at T _N = 30 K. Both magnetoresistance and magnetization measurements have been used to find the behavior of the first order Néel transition. It has been found that the orientation of the field is critical; the Néel is found to decrease only when H is parallel to the b-axis. GdCrSb₃ undergoes a ferrimagnetic transition at T_C = 86 K.; In order to investigate the properties of RCrSb₃ further, LaCrSb₃, PrCrSb₃, and SmCrSb₃ were doped with La and Gd on the rare-earth site. La doping, which has no 4f -electrons, depletes the parent compound of 4f-electrons, while Gd, which has a half full f-shell, increases the number of 4f-electrons. It is found that the average number of 4 f-electrons has important consequences for the family of materials. In addition to the doped materials, the pure compounds are found to all behave in a similar manner and are all displayed on a single phase diagram of transition temperature and average number of 4f-electrons. It is found that the Curie temperature linearly decreases while the Néel temperature quadratically increases as the average number of f-electrons are increased.