Weak ferromagnetism of the layered perovskite (CnH2n+1NH3)2MnCl4(n= 1, 2 and 3)

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Abstract
Weak ferromagnetism in the layered perovskite (C n H2n+1NH3)2MnCl4((n = 1, 2 and 3) has been studied by means of neutron diffraction and SQUID magnetometry. The antiferromagnetic spin arrangement in all the compounds is consistent with the chemical unit cell of the tilt system of MnCl6 octahedra, alternately rotating about the b axis. The weak ferromagnetic moment due to spin canting in the direction of the a axis of the compound with n = 3 is 0.42 × 10−3 μB at 4.2 K; the spin canting can be ascribed to an antisymmetric exchange interaction through a coupling of the spin directions and the tilting directions of the MnCl6 octahedra. The critical index β of the antiferromagnetic moment and that of the weak ferromagnetic moment for this compound are 0.25 + 0.02 and 0.229 + 0.005, respectively; the results reflect the character of the two-dimensional magnetic system. For the compounds with n = 1 and 2 the weak ferromagnetic moments are found in the c-plane.