Magnetic and transport characteristics in Gd0.925La0.075Mn2Ge2 with two-dimensional alignment of Mn atoms -: art. no. 174440

We present our recent experimental results on magnetic and transport properties in intermetallic compound Gd0.925La0.075Mn2Ge2 with the ThCr2Si2-type layered structure. The results obtained indicate that Gd0.925La0.075Mn2Ge2 reveals two kinds of first order transitions below the ferrimagnetic Curie temperature T-t1, from canted ferrimagnetic to noncollinear antiferromagnetic states and from noncollinear antiferromagnetic to reentrant canted ferrimagnetic states at T-t2 and T-t3 with decreasing temperature. Between T-t2 and T-t3, a field induced metamagnetism from noncollinear antiferromagnetism to canted ferrimagnetism appears at relatively lower fields, accompanied with fractal-like multistep transitions, the so called "devil's stair case." Furthermore, a negative giant magnetoresistance effect (Delta rho/rho similar to 15%) is also observed at the field induced metamagnetic transition. The mechanism of this negative GMR is discussed on the basis of the results of comprehensive measurements of the resistivities using single-crystalline Gd0.925La0.075Mn2Ge2 and TbMn2Ge2. These unusual features might be characteristic of layered structure, two-dimensional alignment of Mn atoms.