Magnetic phase diagram and spin glass behavior of Fe1−<i>x</i>Mn<i>x</i>Cl2⋅2H2O

Abstract

The magnetic phase diagram of Fe1−xMnxCl2⋅2H2O has been determined. A tetracritical point appears to be present at x≂0.74 and T≂2.8 K. The upper paramagnetic–antiferromagnetic phase boundaries exhibit an unusually rapid descent, and the mixed ordered region below the tetracritical point is quite small. Moreover, regions exhibiting spin glass character also occur in the diagram. The unusually complex behavior is presumably due to the unique constitution of this system: A mixture of two antiferromagnets with different periodicities, competing orthogonal spin anisotropies, competing ferromagnetic and antiferromagnetic near neighbor intrachain exchange interactions, and substantial next nearest neighbor antiferromagnetic interchain exchange interactions.