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 proper ties 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 antiferromagnet ic states and from noncollinear antiferromagnetic to reentrant canted ferri magnetic states at T-t2 and T-t3 with decreasing temperature. Between T-t2 and T-t3, a field induced metamagnetism from noncollinear antiferromagnetis m 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 sim ilar to 15%) is also observed at the field induced metamagnetic transition. The mechanism of this negative GMR is discussed on the basis of the result s of comprehensive measurements of the resistivities using single-crystalli ne Gd0.925La0.075Mn2Ge2 and TbMn2Ge2. These unusual features might be chara cteristic of layered structure, two-dimensional alignment of Mn atoms.