Correlation between Slanted Magnetic Structure and Electromagnetic Responses in the RAlGe (R = Tb and Er) System

Abstract

The structure, specific heat, and magnetic and transport properties of RAlGe (R = Tb and Er) are systematically studied using X-ray diffraction and magnetic and electric measurements. RAlGe crystallizes in an orthorhombic YAlGe-type structure with a space group of Cmcm (N 63, oS12). RAlGe consists of the slanted magnetic isosceles triangles R3Δ-∇R3 and Ge-Al6-Ge and AlGe2-Al-Ge2Al clusters. TbAlGe exhibits two transitions at T t = 7 K and T N = 39 K, respectively. ErAlGe orders antiferromagnetically at T N = 7 K. The magnetic transitions are related to the slanted R3 magnetic isosceles triangles in the (0kl) basal plane. According to the reported magnetic structure of RAlGa, the arrangement of triangular magnetic moments for RAlGe is suggested to be antiparallel along the direction perpendicular to the (0kl) basal plane in the temperature region of T < T t and along the prism of R3 magnetic isosceles triangle on the (0kl) basal plane before T N, respectively. The antiferromagnetic order is due to the R3Δ↑ and R3∇↓ exchanging interaction. The magnetic transport of RAlGe depends upon its special magnetic structure, which causes the different magnetic scatters for the conducting electron before and after antiferromagnetic transition and also induces a magnetoresistance ratio change from positive to negative.