Competing magnetic correlations and uniaxial anisotropy in (Fe1-xMnx)2AlB2 single crystals

We have succeeded for the first time in synthesizing single crystals of nanolaminated borides (Fe1-xMnx)2AlB2 in the entire Fe-Mn composition range using the Al self -flux method, and have established T -x and H-T magnetic phase diagrams from the results of magnetization measurements. The ferromagnetic correlation of Fe2AlB2 is weakened with the Mn substitution, whereas the antiferromagnetic correlation of Mn2AlB2 is enhanced with the Fe up to x = 0.65. The spin direction in the magnetically ordered states changes from the a to the b axis with increasing Mn concentration and temperature. At x = 0.31-0.46, there are three magnetic phases; ferromagnetic, antiferromagnetic, and intermediate phases in between. At x = 0.65 and 0.74, a spin -flop -like metamagnetic transition was observed at a finite field parallel to the spin direction. These observations indicate that in (Fe1-xMnx)2AlB2 the ferromagnetic and antiferromagnetic correlations coexist and the uniaxial magnetic anisotropy competes between the a and b axes.