Magnetic properties of distorted pyrochlore lattice Mn₂(OD)₃<i>X</i> (<i>X </i>= Cl, Br)

Atacamite family, of which component is M₂(OH)₃X (M:3dmetal, X:halogen) forms geometrical frustrated lattice, and behave in an exotic magnetic states; the ground state of clinoatacamite is coexistence of long-range order and strong spin fluctuation[1]. Atacamite(Cu₂(OH)₃Cl), which is distorted pyrochlore, reported as antiferromagnetic transition at T_N = 9 K[2]. Recently, it is reported that atacamite is regarded as S =1/2 sawtooth chains system, and its magnetic order is represented k = (1/2 0 1/2) [3,4]. We remark atacamite type compounds Mn₂(OH)₃X. Both compounds have two successive transitions below T ~ 3K [5]. Our neutron experiment revealed different magnetic orders on these four phases. The ground state of Mn₂(OD)₃Br is also represented k = (1/2 0 1/2), its magnetic structure have two kind of spin configurations on the saw tooth chains. Spin configurations on other three phases are modulated along the a axis. Successive transition and different k vector imply stronger frustration effect than atacamite. [1] X. G. Zheng et al., PRL 95, 057201 (2005). [2] X. G. Zheng et al., PRB 71, 174404 (2005). [3] L. Heinze et al., Pyhsica B 536, 377-378 (2018). [4] L. Heinze et al., arXiv:1904.07820v1. [5] M. Hagihala et al., J. Phys.: Cond. Matt. 19, 145281 (2007).