Degenerate ground state in the classical pyrochlore antiferromagnet Na3Mn(CO3)2Cl

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American Physical Society
In an ideal classical pyrochlore antiferromagnet without perturbations, an infinite degeneracy in a ground state leads to the absence of magnetic order and a spin-glass transition. Here we present Na3Mn(CO3)2Cl as a new candidate compound where classical spins are coupled antiferromagnetically on the pyrochlore lattice and report its structural and magnetic properties. The temperature dependences of the magnetic susceptibility and heat capacity and the magnetization curve are consistent with those of an S=5/2 pyrochlore lattice antiferromagnet with nearest-neighbor interactions of 2 K. Neither an apparent signature of a spin-glass transition nor magnetic order is detected in magnetization and heat capacity measurements or powder neutron diffraction experiments. On the other hand, antiferromagnetic short-range order of the nearest neighbors is evidenced by the Q dependence of the diffuse scattering which develops around 0.85Å−1. A high degeneracy near the ground state in Na3Mn(CO3)2Cl is supported by the magnetic entropy, estimated as almost 4JK−2mol−1 at 0.5 K. ©2018 American Physical Society
Neutron diffraction, Antiferromagnetism, Specific heat, Pyrochlore, Magnetic properties, Temperature dependence
Nawa, K., Okuyama, D., Avdeev, M., Nojiri, H., Yoshida, M., Ueta, D., Yoshizawa, H., & Sato, T. J. (2018). Degenerate ground state in the classical pyrochlore antiferromagnet Na3Mn(CO3)2Cl. Physical Review B, 98(14), 144426. doi:10.1103/PhysRevB.98.144426